import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.*;;
import java.util.StringTokenizer;
public class zra2
{
    public static void main(String args[])
    {
        FastReader s=new FastReader();
        int t=s.nextInt();
        int i,n,k,arr[],x,sum=0,num=0,temp[],max=-1,count=0;
        while(t>0)
        {
            --t;
            n=s.nextInt();
            k=s.nextInt();
            arr=new int[n];
            temp=new int[n];
            for(i=0;i<n;i++)
            {
                arr[i]=s.nextInt();
                sum=sum+arr[i]%k;
                if(arr[i]%k==0)
                    temp[i]=0;
                else
                    temp[i]=k-(arr[i]%k);
            }
            if(sum==0)
            {
                System.out.println(sum);
                sum=0;
                continue;
            }
            Arrays.sort(temp);
            for(i=n-1;i>0;i--)
            {
                if(temp[i]==temp[i-1])
                    count++;
                else
                {
                    if(count>max)
                    {
                        max=count;
                        num=temp[i];
                    }
                    count=0;
                }
            }
            if(count>max)
            {
                max=count;
                num=temp[i+1];
            }
            System.out.println(max*k+num+1);
            count=0;
            max=-1;
            sum=0;
        }
    }
}

class FastReader
{
    BufferedReader br;
    StringTokenizer st;
    public FastReader()
    {
        br = new BufferedReader(new
        InputStreamReader(System.in));
    }
    String next()
    {
        while (st == null || !st.hasMoreElements())
        {
            try
            {
                st = new StringTokenizer(br.readLine());
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
        }
        return st.nextToken();
    }
    int nextInt()
    {
        return Integer.parseInt(next());
    }
    long nextLong()
    {
        return Long.parseLong(next());
    }
    double nextDouble()
    {
        return Double.parseDouble(next());
    }
    String nextLine()
    {
        String str = "";
        try
        {
            str = br.readLine();
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }
        return str;
    }
}


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.*;;
import java.util.StringTokenizer;
public class zero_remainder_array
{
    public static void main(String args[])
    {
        FastReader s=new FastReader();
        int t=s.nextInt();
        int i,n,k,arr[],x,sum=0,num;
        while(t>0)
        {
            --t;
            n=s.nextInt();
            k=s.nextInt();
            arr=new int[n];
            ArrayList<Integer>temp=new ArrayList<Integer>();
            for(i=0;i<n;i++)
            {
                arr[i]=s.nextInt();
                num=arr[i]%k;
                sum=sum+num;
                if(num==0)
                    temp.add(num);
                else
                    temp.add(k-num);
            }
            //5 10
            //20 100 50 20 100500
            if(sum==0)
            {
                System.out.println(sum);
                sum=0;
                continue;
            }
            Collections.sort(temp);
            i=0;
            x=0;
            while(temp.get(i)==0)
                i++;
            while(true)
            {
                if(temp.get(i)!=x)
                    x++;
                else
                {
                    i++;
                    if(i==temp.size())
                        break;
                    while(temp.get(i)==x)
                    {
                        temp.add(temp.get(i)+k);
                        i++;
                    }
                    x++;
                }
            }
            System.out.println(x+1);
            sum=0;
        }
    }
}
class FastReader
{
    BufferedReader br;
    StringTokenizer st;
    public FastReader()
    {
        br = new BufferedReader(new
        InputStreamReader(System.in));
    }
    String next()
    {
        while (st == null || !st.hasMoreElements())
        {
            try
            {
                st = new StringTokenizer(br.readLine());
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
        }
        return st.nextToken();
    }
    int nextInt()
    {
        return Integer.parseInt(next());
    }
    long nextLong()
    {
        return Long.parseLong(next());
    }
    double nextDouble()
    {
        return Double.parseDouble(next());
    }
    String nextLine()
    {
        String str = "";
        try
        {
            str = br.readLine();
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }
        return str;
    }
}


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.*;;
import java.util.StringTokenizer;
public class zra2
{
    public static void main(String args[])
    {
        FastReader s=new FastReader();
        int t=s.nextInt();
        int i,n,k,arr[],x,sum=0,num=0,temp[],max=-1,count=0;
        while(t>0)
        {
            --t;
            n=s.nextInt();
            k=s.nextInt();
            arr=new int[n];
            temp=new int[n];
            for(i=0;i<n;i++)
            {
                arr[i]=s.nextInt();
                sum=sum+arr[i]%k;
                if(arr[i]%k==0)
                    temp[i]=0;
                else
                    temp[i]=k-(arr[i]%k);
            }
            if(sum==0)
            {
                System.out.println(sum);
                sum=0;
                continue;
            }
            Arrays.sort(temp);
            for(i=n-1;i>0;i--)
            {
                if(temp[i]==0)
                    continue;
                if(temp[i]==temp[i-1])
                    count++;
                else
                {
                    if(count>max)
                    {
                        max=count;
                        num=temp[i];
                    }
                    count=0;
                }
            }
            if(count>max && n>1)
            {
                max=count;
                num=temp[i+1];
            }
            if(n==1)
                max=0;
            System.out.println((long)max*k+(long)(num+1));
            count=0;
            max=-1;
            sum=0;
        }
    }
}
class FastReader
{
    BufferedReader br;
    StringTokenizer st;
    public FastReader()
    {
        br = new BufferedReader(new
        InputStreamReader(System.in));
    }
    String next()
    {
        while (st == null || !st.hasMoreElements())
        {
            try
            {
                st = new StringTokenizer(br.readLine());
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
        }
        return st.nextToken();
    }
    int nextInt()
    {
        return Integer.parseInt(next());
    }
    long nextLong()
    {
        return Long.parseLong(next());
    }
    double nextDouble()
    {
        return Double.parseDouble(next());
    }
    String nextLine()
    {
        String str = "";
        try
        {
            str = br.readLine();
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }
        return str;
    }
}


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.*;;
import java.util.StringTokenizer;
public class zero_remainder_array
{
    public static void main(String args[])
    {
        FastReader s=new FastReader();
        int t=s.nextInt();
        int i,n,k,arr[],x,sum=0,num;
        while(t>0)
        {
            --t;
            n=s.nextInt();
            k=s.nextInt();
            arr=new int[n];
            ArrayList<Integer>temp=new ArrayList<Integer>();
            for(i=0;i<n;i++)
            {
                arr[i]=s.nextInt();
                num=arr[i]%k;
                sum=sum+num;
                if(num==0)
                    temp.add(num);
                else
                    temp.add(k-num);
            }
            //5 10
            //20 100 50 20 100500
            if(sum==0)
            {
                System.out.println(sum);
                sum=0;
                continue;
            }
            Collections.sort(temp);
            i=0;
            x=0;
            while(true)
            {
                if(temp.get(i)!=x)
                    x++;
                else
                {
                    i++;
                    if(i==temp.size())
                        break;
                    while(temp.get(i)==x)
                    {
                        temp.add(temp.get(i)+k);
                        i++;
                    }
                    x++;
                }
            }
            System.out.println(x+1);
            sum=0;
        }
    }
}
class FastReader
{
    BufferedReader br;
    StringTokenizer st;
    public FastReader()
    {
        br = new BufferedReader(new
        InputStreamReader(System.in));
    }
    String next()
    {
        while (st == null || !st.hasMoreElements())
        {
            try
            {
                st = new StringTokenizer(br.readLine());
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
        }
        return st.nextToken();
    }
    int nextInt()
    {
        return Integer.parseInt(next());
    }
    long nextLong()
    {
        return Long.parseLong(next());
    }
    double nextDouble()
    {
        return Double.parseDouble(next());
    }
    String nextLine()
    {
        String str = "";
        try
        {
            str = br.readLine();
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }
        return str;
    }
}


import java.io.*;
import java.util.*;

public class D
{
	static Scanner scan = new Scanner(System.in);
	public static void solve() throws Exception
	{
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer tk = new StringTokenizer(in.readLine());
		int n = Integer.parseInt(tk.nextToken()); //scan.nextInt();
		int k = Integer.parseInt(tk.nextToken()); //scan.nextInt();
		int[] nums = new int[n];
		long sum =0;
		HashMap<Long,Integer> map = new HashMap<>();
		tk = new StringTokenizer(in.readLine());
		for(int i=0;i<n;i++)
		{
			nums[i]=Integer.parseInt(tk.nextToken()); //scan.nextInt();
			if(nums[i]%k!=0)
			{
				long v = k-nums[i]%k;
				if(map.containsKey(v))
				{
					map.replace(v,map.get(v)+1);
				}
				else
					map.put(v,1);
			}
		}
		long x=0;
		while(true)
		{
			if(map.size()==0)
				break;
			if(map.containsKey(x))
			{
				int a = map.get(x)-1;
				if(a!=0)
					map.put(x+k,a);
				map.remove(x);
				x+=1;
			}
			else
				x+=1;
		}
		System.out.println(x);
	}
	public static void main(String[] args) throws Exception
	{
		if(scan.hasNext())
		{
			int t= scan.nextInt();
			//int t= 1;
			outer:while(t-->0)
			{
				solve();
			}
		}
	}
}


import java.io.*;
import java.util.*;

public class D
{
	static Scanner scan = new Scanner(System.in);
	public static void solve() throws Exception
	{
		//BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		//StringTokenizer tk = new StringTokenizer(in.readLine());
		int n = scan.nextInt();
		int k = scan.nextInt();
		int[] nums = new int[n];
		long sum =0;
		long c=0;
		HashMap<Long,Integer> map = new HashMap<>();
		HashSet<Long> h = new HashSet<>();
		for(int i=0;i<n;i++)
		{
			nums[i]=scan.nextInt();
			if(nums[i]%k!=0)
			{
				c+=1;
				long v = k-nums[i]%k;
				if(map.containsKey(v))
				{
					map.replace(v,map.get(v)+1);
					h.add(v+(map.get(v)-1)*k);
				}
				else
				{
					map.put(v,1);
					h.add(v);
				}
			}
		}
		long x=0;
		long b=0;
		while(true)
		{
			if(b==c)
				break;
			if(map.containsKey(x))
			{
				b+=1;
				int a = map.get(x)-1;
				if(a!=0)
					map.put(x+k,a);
				x+=1;
			}
			else
				x+=1;
		}
		System.out.println(x);
		/*
		Iterator v = h.iterator();
		long max = -1;
		while(v.hasNext())
		{
			long a = (long)v.next();
			max = Math.max(a,max);
		}
		System.out.println(max+1);
		*/
	}
	public static void main(String[] args) throws Exception
	{
		if(scan.hasNext())
		{
			int t= scan.nextInt();
			//int t= 1;
			outer:while(t-->0)
			{
				solve();
			}
		}
	}
}


import java.io.*;
import java.util.*;

public class D
{
	static Scanner scan = new Scanner(System.in);
	public static void solve() throws Exception
	{
		//BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		//StringTokenizer tk = new StringTokenizer(in.readLine());
		int n = scan.nextInt();
		int k = scan.nextInt();
		int[] nums = new int[n];
		long sum =0;
		HashMap<Long,Integer> map = new HashMap<>();
		HashSet<Long> h = new HashSet<>();
		for(int i=0;i<n;i++)
		{
			nums[i]=scan.nextInt();
			if(nums[i]%k!=0)
			{
				long v = k-nums[i]%k;
				if(map.containsKey(v))
				{
					map.replace(v,map.get(v)+1);
					h.add(v+(map.get(v)-1)*k);
				}
				else
				{
					map.put(v,1);
					h.add(v);
				}
			}
		}
		long x=0;
		/*
		while(true)
		{
			if(map.size()==0)
				break;
			if(map.containsKey(x))
			{
				int a = map.get(x)-1;
				if(a!=0)
					map.put(x+k,a);
				map.remove(x);
				x+=1;
			}
			else
				x+=1;
		}
		*/
		Iterator v = h.iterator();
		long max = -1;
		while(v.hasNext())
		{
			long a = (long)v.next();
			max = Math.max(a,max);
		}
		System.out.println(max+1);
	}
	public static void main(String[] args) throws Exception
	{
		if(scan.hasNext())
		{
			int t= scan.nextInt();
			//int t= 1;
			outer:while(t-->0)
			{
				solve();
			}
		}
	}
}


import java.io.*;
import java.util.*;

public class Main
{
	static Scanner scan = new Scanner(System.in);
	public static void solve() throws Exception
	{
		//BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		//StringTokenizer tk = new StringTokenizer(in.readLine());
		int n = scan.nextInt();
		long k = scan.nextLong();
		int[] nums = new int[n];
		long sum =0;
		HashMap<Long,Long> map = new HashMap<>();
		HashSet<Long> h = new HashSet<>();
		for(int i=0;i<n;i++)
		{
			nums[i]=scan.nextInt();
			if(nums[i]%k!=0)
			{
				long v = k-nums[i]%k;
				if(map.containsKey(v))
				{
					map.replace(v,map.get(v)+1);
					h.add(v+(map.get(v)-1)*k);
				}
				else
				{
					map.put(v,(long)1);
					h.add(v);
				}
			}
		}
		long x=0;
		/*
		while(true)
		{
			if(map.size()==0)
				break;
			if(map.containsKey(x))
			{
				int a = map.get(x)-1;
				if(a!=0)
					map.put(x+k,a);
				map.remove(x);
				x+=1;
			}
			else
				x+=1;
		}
		*/
		Iterator v = h.iterator();
		long max = -1;
		while(v.hasNext())
		{
			long a = (long)v.next();
			max = Math.max(a,max);
		}
		System.out.println(max+1);
	}
	public static void main(String[] args) throws Exception
	{
		if(scan.hasNext())
		{
			int t= scan.nextInt();
			//int t= 1;
			outer:while(t-->0)
			{
				solve();
			}
		}
	}
}


import java.io.*;
import java.util.*;

public class D
{
	static Scanner scan = new Scanner(System.in);
	public static void solve() throws Exception
	{
		//BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		//StringTokenizer tk = new StringTokenizer(in.readLine());
		int n = scan.nextInt();
		int k = scan.nextInt();
		int[] nums = new int[n];
		long sum =0;
		HashMap<Long,Integer> map = new HashMap<>();
		HashSet<Long> h = new HashSet<>();
		for(int i=0;i<n;i++)
		{
			nums[i]=scan.nextInt();
			if(nums[i]%k!=0)
			{
				long v = k-nums[i]%k;
				if(map.containsKey(v))
				{
					map.replace(v,map.get(v)+1);
					h.add(v+(map.get(v)-1)*k);
				}
				else
				{
					map.put(v,1);
					h.add(v);
				}
			}
		}
		long x=0;
		/*
		while(true)
		{
			if(map.size()==0)
				break;
			if(map.containsKey(x))
			{
				int a = map.get(x)-1;
				if(a!=0)
					map.put(x+k,a);
				map.remove(x);
				x+=1;
			}
			else
				x+=1;
		}
		*/
		while(true)
		{
			if(h.size()==0)
			{
				break;
			}
			if(h.contains(x))
			{
				h.remove(x);
				x+=1;
			}
			else
				x+=1;
		}
		System.out.println(x);
	}
	public static void main(String[] args) throws Exception
	{
		if(scan.hasNext())
		{
			int t= scan.nextInt();
			//int t= 1;
			outer:while(t-->0)
			{
				solve();
			}
		}
	}
}


import java.io.*;
import java.util.*;

public class D
{
	static Scanner scan = new Scanner(System.in);
	public static void solve() throws Exception
	{
		//BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		//StringTokenizer tk = new StringTokenizer(in.readLine());
		int n = scan.nextInt();
		int k = scan.nextInt();
		int[] nums = new int[n];
		long sum =0;
		HashMap<Long,Integer> map = new HashMap<>();
		for(int i=0;i<n;i++)
		{
			nums[i]=scan.nextInt();
			if(nums[i]%k!=0)
			{
				long v = k-nums[i]%k;
				if(map.containsKey(v))
				{
					map.replace(v,map.get(v)+1);
				}
				else
					map.put(v,1);
			}
		}
		long x=0;
		while(true)
		{
			if(map.size()==0)
				break;
			if(map.containsKey(x))
			{
				int a = map.get(x)-1;
				if(a!=0)
					map.put(x+k,a);
				map.remove(x);
				x+=1;
			}
			else
				x+=1;
		}
		System.out.println(x);
	}
	public static void main(String[] args) throws Exception
	{
		if(scan.hasNext())
		{
			int t= scan.nextInt();
			//int t= 1;
			outer:while(t-->0)
			{
				solve();
			}
		}
	}
}


import java.io.*;
import java.util.*;
import java.lang.*;

public class ZeroRemainderArray{
    public static class FastReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private SpaceCharFilter filter;
        public FastReader(InputStream stream) {
            this.stream = stream;
        }
        public int read() {
            if (numChars==-1)
                throw new InputMismatchException();
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                }
                catch (IOException e) {
                    throw new InputMismatchException();
                }
                if(numChars <= 0)
                    return -1;
            }
            return buf[curChar++];
        }
        public String nextLine() {
            BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
            String str = "";
            try {
                str = br.readLine();
            }
            catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
        public int nextInt() {
            int c = read();
            while(isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do {
                if(c<'0'||c>'9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            }
            while (!isSpaceChar(c));
            return res * sgn;
        }
        public long nextLong() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;
            do {
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            }
            while (!isSpaceChar(c));
            return res * sgn;
        }
        public double nextDouble() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            double res = 0;
            while (!isSpaceChar(c) && c != '.') {
                if (c == 'e' || c == 'E')
                    return res * Math.pow(10, nextInt());
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            }
            if (c == '.') {
                c = read();
                double m = 1;
                while (!isSpaceChar(c))
                {
                    if (c == 'e' || c == 'E')
                        return res * Math.pow(10, nextInt());
                    if (c < '0' || c > '9')
                        throw new InputMismatchException();
                    m /= 10;
                    res += (c - '0') * m;
                    c = read();
                }
            }
            return res * sgn;
        }
        public char nextChar() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            return (char)c;
        }
        public String next() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            }
            while (!isSpaceChar(c));
            return res.toString();
        }
        public boolean isSpaceChar(int c) {
            if (filter != null)
                return filter.isSpaceChar(c);
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }
        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);
        }
    }
    static long gcd(long a, long b){
        if (a == 0)
            return b;
        return gcd(b % a, a);
    }
    static long lcm(long a, long b)  {
        return (a*b)/gcd(a, b);
    }
    static long func(long a[],long size,int s){
        long max1=a[s];
        long maxc=a[s];
        for(int i=s+1;i<size;i++){
            maxc=Math.max(a[i],maxc+a[i]);
            max1=Math.max(maxc,max1);
        }
        return max1;
    }
    public static class Pair<U extends Comparable<U>, V extends Comparable<V>> implements Comparable<Pair<U, V>> {
        public U x;
        public V y;

        public Pair(U x, V y) {
            this.x = x;
            this.y = y;
        }

        public int hashCode() {
            return (x == null ? 0 : x.hashCode() * 31) + (y == null ? 0 : y.hashCode());
        }

        public boolean equals(Object o) {
            if (this == o)
                return true;
            if (o == null || getClass() != o.getClass())
                return false;
            Pair<U, V> p = (Pair<U, V>) o;
            return (x == null ? p.x == null : x.equals(p.x)) && (y == null ? p.y == null : y.equals(p.y));
        }

        public int compareTo(Pair<U, V> b) {
            int cmpU = x.compareTo(b.x);
            return cmpU != 0 ? cmpU : y.compareTo(b.y);
        }

        public String toString() {
            return String.format("(%s, %s)", x.toString(), y.toString());
        }

    }

    public static void main(String args[])
    {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        FastReader sc = new FastReader(inputStream);
        PrintWriter w = new PrintWriter(outputStream);

        int t = sc.nextInt();
        while(t-- > 0)
        {
        	int n = sc.nextInt();
        	int k = sc.nextInt();
        	int a[] = new int[n];
        	int temp[] = new int[n];
        	HashMap<Integer,Integer> hm = new HashMap<>();

        	for(int i = 0; i < n; i++)
        	{
        		a[i] = sc.nextInt();
        	}

        	int div = 0;
        	for(int i = 0; i < n; i++)
        	{
        		temp[i] = a[i]%k;
        		if(temp[i] == 0)
        		{
        			div++;
        		}
        		temp[i] = k - temp[i];
        	}

        	if(div == n)
        	{
        		w.println(0);
        		continue;
        	}

        	Arrays.sort(temp);
        	int max = 1,count = 1, maxelement = 0;

        	for(int i = n-1; i >= 0; i--)
        	{
                if(temp[i] != k)
                {
                    maxelement = temp[i];
                    break;
                }
            }

        	for(int i = 0; i < n-1; i++)
        	{
        		if(temp[i] == k)
        		{
        			break;
        		}
        		if(temp[i] == temp[i+1])
        		{
        			count++;
        			if(max <= count)
        			{
        				max = count;
        				maxelement = temp[i];
        			}
        		}
        		else
        		{
        			count = 1;
        		}
        	}

        	long x = max - 1;
        	long ans = x*k;
        	ans += maxelement;

        	w.println(++ans);

        }
        w.close();
    }
}


import java.io.*;
import java.util.*;
import java.lang.*;

public class ZeroRemainderArray{
    public static class FastReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private SpaceCharFilter filter;
        public FastReader(InputStream stream) {
            this.stream = stream;
        }
        public int read() {
            if (numChars==-1)
                throw new InputMismatchException();
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                }
                catch (IOException e) {
                    throw new InputMismatchException();
                }
                if(numChars <= 0)
                    return -1;
            }
            return buf[curChar++];
        }
        public String nextLine() {
            BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
            String str = "";
            try {
                str = br.readLine();
            }
            catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
        public int nextInt() {
            int c = read();
            while(isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do {
                if(c<'0'||c>'9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            }
            while (!isSpaceChar(c));
            return res * sgn;
        }
        public long nextLong() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;
            do {
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            }
            while (!isSpaceChar(c));
            return res * sgn;
        }
        public double nextDouble() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            double res = 0;
            while (!isSpaceChar(c) && c != '.') {
                if (c == 'e' || c == 'E')
                    return res * Math.pow(10, nextInt());
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            }
            if (c == '.') {
                c = read();
                double m = 1;
                while (!isSpaceChar(c))
                {
                    if (c == 'e' || c == 'E')
                        return res * Math.pow(10, nextInt());
                    if (c < '0' || c > '9')
                        throw new InputMismatchException();
                    m /= 10;
                    res += (c - '0') * m;
                    c = read();
                }
            }
            return res * sgn;
        }
        public char nextChar() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            return (char)c;
        }
        public String next() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            }
            while (!isSpaceChar(c));
            return res.toString();
        }
        public boolean isSpaceChar(int c) {
            if (filter != null)
                return filter.isSpaceChar(c);
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }
        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);
        }
    }
    static long gcd(long a, long b){
        if (a == 0)
            return b;
        return gcd(b % a, a);
    }
    static long lcm(long a, long b)  {
        return (a*b)/gcd(a, b);
    }
    static long func(long a[],long size,int s){
        long max1=a[s];
        long maxc=a[s];
        for(int i=s+1;i<size;i++){
            maxc=Math.max(a[i],maxc+a[i]);
            max1=Math.max(maxc,max1);
        }
        return max1;
    }
    public static class Pair<U extends Comparable<U>, V extends Comparable<V>> implements Comparable<Pair<U, V>> {
        public U x;
        public V y;

        public Pair(U x, V y) {
            this.x = x;
            this.y = y;
        }

        public int hashCode() {
            return (x == null ? 0 : x.hashCode() * 31) + (y == null ? 0 : y.hashCode());
        }

        public boolean equals(Object o) {
            if (this == o)
                return true;
            if (o == null || getClass() != o.getClass())
                return false;
            Pair<U, V> p = (Pair<U, V>) o;
            return (x == null ? p.x == null : x.equals(p.x)) && (y == null ? p.y == null : y.equals(p.y));
        }

        public int compareTo(Pair<U, V> b) {
            int cmpU = x.compareTo(b.x);
            return cmpU != 0 ? cmpU : y.compareTo(b.y);
        }

        public String toString() {
            return String.format("(%s, %s)", x.toString(), y.toString());
        }

    }

    public static void main(String args[])
    {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        FastReader sc = new FastReader(inputStream);
        PrintWriter w = new PrintWriter(outputStream);

        int t = sc.nextInt();
        while(t-- > 0)
        {
        	int n = sc.nextInt();
        	int k = sc.nextInt();
        	int a[] = new int[n];
        	int c = 0;

        	HashMap<Integer,Integer> hm = new HashMap<>();

        	for(int i = 0; i < n; i++)
        	{
        		a[i] = sc.nextInt();
        		int temp = a[i] % k;

        		if(temp == 0)
        		{
        			c++;
        		}

        		temp = k - temp;
        		if(hm.containsKey(temp))
        		{
        			hm.put(temp, hm.get(temp) + 1);
        		}
        		else
        		{
        			hm.put(temp, 1);
        		}
        	}

        	//w.println(hm);

        	if(c == n)
        	{
        		w.println("0");
        		continue;
        	}

        	long count = 0;
        	for(int i : hm.keySet())
        	{
        		if(i != 0)
        		{
        			if(hm.get(i) - 1 > 0)
        			{
        				i += (hm.get(i) - 1)*k;
        			}
        			count = Math.max(count, i);
        		}
        	}

        	if(hm.size() == n)
        	{
        		w.println(count);
        	}
        	else
        	{
        		w.println(++count);
        	}
        }
        w.close();
    }
}


import java.io.*;
import java.util.*;
import java.lang.*;

public class ZeroRemainderArray{
    public static class FastReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private SpaceCharFilter filter;
        public FastReader(InputStream stream) {
            this.stream = stream;
        }
        public int read() {
            if (numChars==-1)
                throw new InputMismatchException();
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                }
                catch (IOException e) {
                    throw new InputMismatchException();
                }
                if(numChars <= 0)
                    return -1;
            }
            return buf[curChar++];
        }
        public String nextLine() {
            BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
            String str = "";
            try {
                str = br.readLine();
            }
            catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
        public int nextInt() {
            int c = read();
            while(isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do {
                if(c<'0'||c>'9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            }
            while (!isSpaceChar(c));
            return res * sgn;
        }
        public long nextLong() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;
            do {
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            }
            while (!isSpaceChar(c));
            return res * sgn;
        }
        public double nextDouble() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            double res = 0;
            while (!isSpaceChar(c) && c != '.') {
                if (c == 'e' || c == 'E')
                    return res * Math.pow(10, nextInt());
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            }
            if (c == '.') {
                c = read();
                double m = 1;
                while (!isSpaceChar(c))
                {
                    if (c == 'e' || c == 'E')
                        return res * Math.pow(10, nextInt());
                    if (c < '0' || c > '9')
                        throw new InputMismatchException();
                    m /= 10;
                    res += (c - '0') * m;
                    c = read();
                }
            }
            return res * sgn;
        }
        public char nextChar() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            return (char)c;
        }
        public String next() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            }
            while (!isSpaceChar(c));
            return res.toString();
        }
        public boolean isSpaceChar(int c) {
            if (filter != null)
                return filter.isSpaceChar(c);
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }
        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);
        }
    }
    static long gcd(long a, long b){
        if (a == 0)
            return b;
        return gcd(b % a, a);
    }
    static long lcm(long a, long b)  {
        return (a*b)/gcd(a, b);
    }
    static long func(long a[],long size,int s){
        long max1=a[s];
        long maxc=a[s];
        for(int i=s+1;i<size;i++){
            maxc=Math.max(a[i],maxc+a[i]);
            max1=Math.max(maxc,max1);
        }
        return max1;
    }
    public static class Pair<U extends Comparable<U>, V extends Comparable<V>> implements Comparable<Pair<U, V>> {
        public U x;
        public V y;

        public Pair(U x, V y) {
            this.x = x;
            this.y = y;
        }

        public int hashCode() {
            return (x == null ? 0 : x.hashCode() * 31) + (y == null ? 0 : y.hashCode());
        }

        public boolean equals(Object o) {
            if (this == o)
                return true;
            if (o == null || getClass() != o.getClass())
                return false;
            Pair<U, V> p = (Pair<U, V>) o;
            return (x == null ? p.x == null : x.equals(p.x)) && (y == null ? p.y == null : y.equals(p.y));
        }

        public int compareTo(Pair<U, V> b) {
            int cmpU = x.compareTo(b.x);
            return cmpU != 0 ? cmpU : y.compareTo(b.y);
        }

        public String toString() {
            return String.format("(%s, %s)", x.toString(), y.toString());
        }

    }

    public static void main(String args[])
    {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        FastReader sc = new FastReader(inputStream);
        PrintWriter w = new PrintWriter(outputStream);

        int t = sc.nextInt();
        while(t-- > 0)
        {
        	int n = sc.nextInt();
        	int k = sc.nextInt();
        	int a[] = new int[n];

        	HashMap<Integer,Integer> hm = new HashMap<>();

        	for(int i = 0; i < n; i++)
        	{
        		a[i] = sc.nextInt();
        		int temp = a[i] % k;

        		if(hm.containsKey(temp))
        		{
        			hm.put(temp, hm.get(temp) + 1);
        		}
        		else
        		{
        			hm.put(temp, 1);
        		}
        	}

        	//w.println(hm);
        	int c = 0;
        	for(int i = 0; i < n; i++)
        	{
        		if(a[i] % k == 0)
        		{
        			c++;
        		}
        	}
        	if(c == n)
        	{
        		w.println("0");
        		continue;
        	}

        	int count = 0;
        	for(int i : hm.keySet())
        	{
        		int temp = hm.get(i)*k - i;
        		count = Math.max(count, temp);
        	}

        	if(hm.size() == n)
        	{
        		w.println(count);
        	}
        	else
        	{
            	w.println(++count);
        	}
        }
        w.close();
    }
}


import java.io.*;
import java.util.*;
import java.lang.*;

public class ZeroRemainderArray{
    public static class FastReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private SpaceCharFilter filter;
        public FastReader(InputStream stream) {
            this.stream = stream;
        }
        public int read() {
            if (numChars==-1)
                throw new InputMismatchException();
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                }
                catch (IOException e) {
                    throw new InputMismatchException();
                }
                if(numChars <= 0)
                    return -1;
            }
            return buf[curChar++];
        }
        public String nextLine() {
            BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
            String str = "";
            try {
                str = br.readLine();
            }
            catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
        public int nextInt() {
            int c = read();
            while(isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do {
                if(c<'0'||c>'9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            }
            while (!isSpaceChar(c));
            return res * sgn;
        }
        public long nextLong() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;
            do {
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            }
            while (!isSpaceChar(c));
            return res * sgn;
        }
        public double nextDouble() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            double res = 0;
            while (!isSpaceChar(c) && c != '.') {
                if (c == 'e' || c == 'E')
                    return res * Math.pow(10, nextInt());
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            }
            if (c == '.') {
                c = read();
                double m = 1;
                while (!isSpaceChar(c))
                {
                    if (c == 'e' || c == 'E')
                        return res * Math.pow(10, nextInt());
                    if (c < '0' || c > '9')
                        throw new InputMismatchException();
                    m /= 10;
                    res += (c - '0') * m;
                    c = read();
                }
            }
            return res * sgn;
        }
        public char nextChar() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            return (char)c;
        }
        public String next() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            }
            while (!isSpaceChar(c));
            return res.toString();
        }
        public boolean isSpaceChar(int c) {
            if (filter != null)
                return filter.isSpaceChar(c);
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }
        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);
        }
    }
    static long gcd(long a, long b){
        if (a == 0)
            return b;
        return gcd(b % a, a);
    }
    static long lcm(long a, long b)  {
        return (a*b)/gcd(a, b);
    }
    static long func(long a[],long size,int s){
        long max1=a[s];
        long maxc=a[s];
        for(int i=s+1;i<size;i++){
            maxc=Math.max(a[i],maxc+a[i]);
            max1=Math.max(maxc,max1);
        }
        return max1;
    }
    public static class Pair<U extends Comparable<U>, V extends Comparable<V>> implements Comparable<Pair<U, V>> {
        public U x;
        public V y;

        public Pair(U x, V y) {
            this.x = x;
            this.y = y;
        }

        public int hashCode() {
            return (x == null ? 0 : x.hashCode() * 31) + (y == null ? 0 : y.hashCode());
        }

        public boolean equals(Object o) {
            if (this == o)
                return true;
            if (o == null || getClass() != o.getClass())
                return false;
            Pair<U, V> p = (Pair<U, V>) o;
            return (x == null ? p.x == null : x.equals(p.x)) && (y == null ? p.y == null : y.equals(p.y));
        }

        public int compareTo(Pair<U, V> b) {
            int cmpU = x.compareTo(b.x);
            return cmpU != 0 ? cmpU : y.compareTo(b.y);
        }

        public String toString() {
            return String.format("(%s, %s)", x.toString(), y.toString());
        }

    }

    public static void main(String args[])
    {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        FastReader sc = new FastReader(inputStream);
        PrintWriter w = new PrintWriter(outputStream);

        int t = sc.nextInt();
        while(t-- > 0)
        {
        	int n = sc.nextInt();
        	int k = sc.nextInt();
        	int a[] = new int[n];

        	HashMap<Integer,Integer> hm = new HashMap<>();

        	for(int i = 0; i < n; i++)
        	{
        		a[i] = sc.nextInt();
        		int temp = a[i] % k;

        		if(hm.containsKey(temp))
        		{
        			hm.put(temp, hm.get(temp) + 1);
        		}
        		else
        		{
        			hm.put(temp, 1);
        		}
        	}

        	//w.println(hm);
        	int c = 0;
        	for(int i = 0; i < n; i++)
        	{
        		if(a[i] % k == 0)
        		{
        			c++;
        		}
        	}
        	if(c == n)
        	{
        		w.println("0");
        		continue;
        	}

        	long count = 0;
        	for(int i : hm.keySet())
        	{
        		if(i != 0)
        		{
            		long temp = hm.get(i)*k - i;
            		count = Math.max(count, temp);
        		}
        	}

        	w.println(++count);
        }
        w.close();
    }
}


import java.io.*;
import java.util.*;
import java.lang.*;

public class ZeroRemainderArray{
    public static class FastReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private SpaceCharFilter filter;
        public FastReader(InputStream stream) {
            this.stream = stream;
        }
        public int read() {
            if (numChars==-1)
                throw new InputMismatchException();
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                }
                catch (IOException e) {
                    throw new InputMismatchException();
                }
                if(numChars <= 0)
                    return -1;
            }
            return buf[curChar++];
        }
        public String nextLine() {
            BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
            String str = "";
            try {
                str = br.readLine();
            }
            catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
        public int nextInt() {
            int c = read();
            while(isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do {
                if(c<'0'||c>'9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            }
            while (!isSpaceChar(c));
            return res * sgn;
        }
        public long nextLong() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;
            do {
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            }
            while (!isSpaceChar(c));
            return res * sgn;
        }
        public double nextDouble() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            double res = 0;
            while (!isSpaceChar(c) && c != '.') {
                if (c == 'e' || c == 'E')
                    return res * Math.pow(10, nextInt());
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            }
            if (c == '.') {
                c = read();
                double m = 1;
                while (!isSpaceChar(c))
                {
                    if (c == 'e' || c == 'E')
                        return res * Math.pow(10, nextInt());
                    if (c < '0' || c > '9')
                        throw new InputMismatchException();
                    m /= 10;
                    res += (c - '0') * m;
                    c = read();
                }
            }
            return res * sgn;
        }
        public char nextChar() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            return (char)c;
        }
        public String next() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            }
            while (!isSpaceChar(c));
            return res.toString();
        }
        public boolean isSpaceChar(int c) {
            if (filter != null)
                return filter.isSpaceChar(c);
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }
        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);
        }
    }
    static long gcd(long a, long b){
        if (a == 0)
            return b;
        return gcd(b % a, a);
    }
    static long lcm(long a, long b)  {
        return (a*b)/gcd(a, b);
    }
    static long func(long a[],long size,int s){
        long max1=a[s];
        long maxc=a[s];
        for(int i=s+1;i<size;i++){
            maxc=Math.max(a[i],maxc+a[i]);
            max1=Math.max(maxc,max1);
        }
        return max1;
    }
    public static class Pair<U extends Comparable<U>, V extends Comparable<V>> implements Comparable<Pair<U, V>> {
        public U x;
        public V y;

        public Pair(U x, V y) {
            this.x = x;
            this.y = y;
        }

        public int hashCode() {
            return (x == null ? 0 : x.hashCode() * 31) + (y == null ? 0 : y.hashCode());
        }

        public boolean equals(Object o) {
            if (this == o)
                return true;
            if (o == null || getClass() != o.getClass())
                return false;
            Pair<U, V> p = (Pair<U, V>) o;
            return (x == null ? p.x == null : x.equals(p.x)) && (y == null ? p.y == null : y.equals(p.y));
        }

        public int compareTo(Pair<U, V> b) {
            int cmpU = x.compareTo(b.x);
            return cmpU != 0 ? cmpU : y.compareTo(b.y);
        }

        public String toString() {
            return String.format("(%s, %s)", x.toString(), y.toString());
        }

    }

    public static void main(String args[])
    {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        FastReader sc = new FastReader(inputStream);
        PrintWriter w = new PrintWriter(outputStream);

        int t = sc.nextInt();
        while(t-- > 0)
        {
        	int n = sc.nextInt();
        	int k = sc.nextInt();
        	int a[] = new int[n];

        	HashMap<Integer,Integer> hm = new HashMap<>();

        	for(int i = 0; i < n; i++)
        	{
        		a[i] = sc.nextInt();
        		int temp = a[i] % k;

        		if(hm.containsKey(temp))
        		{
        			hm.put(temp, hm.get(temp) + 1);
        		}
        		else
        		{
        			hm.put(temp, 1);
        		}
        	}

        	//w.println(hm);
        	int c = 0;
        	for(int i = 0; i < n; i++)
        	{
        		if(a[i] % k == 0)
        		{
        			c++;
        		}
        	}
        	if(c == n)
        	{
        		w.println("0");
        		continue;
        	}

        	int count = 0;
        	for(int i : hm.keySet())
        	{
        		if(i != 0)
        		{
            		int temp = hm.get(i)*k - i;
            		count = Math.max(count, temp);
        		}
        	}

        	w.println(++count);
        }
        w.close();
    }
}


/*   盗图小能手
⣿⣿⣿⣿⣿⣿⡷⣯⢿⣿⣷⣻⢯⣿⡽⣻⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣇⠸⣿⣿⣆⠹⣿⣿⢾⣟⣯⣿⣿⣿⣿⣿⣿⣽⣻⣿⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣻⣽⡿⣿⣎⠙⣿⣞⣷⡌⢻⣟⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⣿⣿⣿⣿⣿⣿⡄⠹⣿⣿⡆⠻⣿⣟⣯⡿⣽⡿⣿⣿⣿⣿⣽⡷⣯⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣟⣷⣿⣿⣿⡀⠹⣟⣾⣟⣆⠹⣯⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡇⢠⡘⣿⣿⡄⠉⢿⣿⣽⡷⣿⣻⣿⣿⣿⣿⡝⣷⣯⢿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣯⢿⣾⢿⣿⡄⢄⠘⢿⣞⡿⣧⡈⢷⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡇⢸⣧⠘⣿⣷⠈⣦⠙⢿⣽⣷⣻⣽⣿⣿⣿⣿⣌⢿⣯⢿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣟⣯⣿⢿⣿⡆⢸⡷⡈⢻⡽⣷⡷⡄⠻⣽⣿⣿⡿⣿⣿⣿⣿⣿⣿⣷⣿⣿⣿⣿⣏⢰⣯⢷⠈⣿⡆⢹⢷⡌⠻⡾⢋⣱⣯⣿⣿⣿⣿⡆⢻⡿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⡎⣿⢾⡿⣿⡆⢸⣽⢻⣄⠹⣷⣟⣿⣄⠹⣟⣿⣿⣟⣿⣿⣿⣿⣿⣿⣽⣿⣿⣿⡇⢸⣯⣟⣧⠘⣷⠈⡯⠛⢀⡐⢾⣟⣷⣻⣿⣿⣿⡿⡌⢿⣻⣿⣿
⣿⣿⣿⣿⣿⣿⣧⢸⡿⣟⣿⡇⢸⣯⣟⣮⢧⡈⢿⣞⡿⣦⠘⠏⣹⣿⣽⢿⣿⣿⣿⣿⣯⣿⣿⣿⡇⢸⣿⣿⣾⡆⠹⢀⣠⣾⣟⣷⡈⢿⣞⣯⢿⣿⣿⣿⢷⠘⣯⣿⣿
⣿⣿⣿⣿⣿⣿⣿⡈⣿⢿⣽⡇⠘⠛⠛⠛⠓⠓⠈⠛⠛⠟⠇⢀⢿⣻⣿⣯⢿⣿⣿⣿⣷⢿⣿⣿⠁⣾⣿⣿⣿⣧⡄⠇⣹⣿⣾⣯⣿⡄⠻⣽⣯⢿⣻⣿⣿⡇⢹⣾⣿
⣿⣿⣿⣿⣿⣿⣿⡇⢹⣿⡽⡇⢸⣿⣿⣿⣿⣿⣞⣆⠰⣶⣶⡄⢀⢻⡿⣯⣿⡽⣿⣿⣿⢯⣟⡿⢀⣿⣿⣿⣿⣿⣧⠐⣸⣿⣿⣷⣿⣿⣆⠹⣯⣿⣻⣿⣿⣿⢀⣿⢿
⣿⣿⣿⣿⣿⣿⣿⣿⠘⣯⡿⡇⢸⣿⣿⣿⣿⣿⣿⣿⣧⡈⢿⣳⠘⡄⠻⣿⢾⣽⣟⡿⣿⢯⣿⡇⢸⣿⣿⣿⣿⣿⣿⡀⢾⣿⣿⣿⣿⣿⣿⣆⠹⣾⣷⣻⣿⡿⡇⢸⣿
⣿⣿⣿⣿⣿⣿⣿⣿⡇⢹⣿⠇⢸⣿⣿⣿⣿⣿⣿⣿⣿⣷⣄⠻⡇⢹⣆⠹⣟⣾⣽⣻⣟⣿⣽⠁⣾⣿⣿⣿⣿⣿⣿⣇⣿⣿⠿⠛⠛⠉⠙⠋⢀⠁⢘⣯⣿⣿⣧⠘⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⡈⣿⡃⢼⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣦⡙⠌⣿⣆⠘⣿⣞⡿⣞⡿⡞⢠⣿⣿⣿⣿⣿⡿⠛⠉⠁⢀⣀⣠⣤⣤⣶⣶⣶⡆⢻⣽⣞⡿⣷⠈⣿
⣿⣿⣿⣿⣿⣿⣿⣿⡿⠃⠘⠁⠉⠉⠉⠉⠉⠉⠉⠉⠉⠙⠛⠛⢿⣄⢻⣿⣧⠘⢯⣟⡿⣽⠁⣾⣿⣿⣿⣿⣿⡃⢀⢀⠘⠛⠿⢿⣻⣟⣯⣽⣻⣵⡀⢿⣯⣟⣿⢀⣿
⣿⣿⣿⣟⣿⣿⣿⣿⣶⣶⡆⢀⣿⣾⣿⣾⣷⣿⣶⠿⠚⠉⢀⢀⣤⣿⣷⣿⣿⣷⡈⢿⣻⢃⣼⣿⣿⣿⣿⣻⣿⣿⣿⡶⣦⣤⣄⣀⡀⠉⠛⠛⠷⣯⣳⠈⣾⡽⣾⢀⣿
⣿⢿⣿⣿⣻⣿⣿⣿⣿⣿⡿⠐⣿⣿⣿⣿⠿⠋⠁⢀⢀⣤⣾⣿⣿⣿⣿⣿⣿⣿⣿⣌⣥⣾⡿⣿⣿⣷⣿⣿⢿⣷⣿⣿⣟⣾⣽⣳⢯⣟⣶⣦⣤⡾⣟⣦⠘⣿⢾⡁⢺
⣿⣻⣿⣿⡷⣿⣿⣿⣿⣿⡗⣦⠸⡿⠋⠁⢀⢀⣠⣴⢿⣿⣽⣻⢽⣾⣟⣷⣿⣟⣿⣿⣿⣳⠿⣵⣧⣼⣿⣿⣿⣿⣿⣾⣿⣿⣿⣿⣿⣽⣳⣯⣿⣿⣿⣽⢀⢷⣻⠄⠘
⣿⢷⣻⣿⣿⣷⣻⣿⣿⣿⡷⠛⣁⢀⣀⣤⣶⣿⣛⡿⣿⣮⣽⡻⣿⣮⣽⣻⢯⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣯⢀⢸⣿⢀⡆
⠸⣟⣯⣿⣿⣷⢿⣽⣿⣿⣷⣿⣷⣆⠹⣿⣶⣯⠿⣿⣶⣟⣻⢿⣷⣽⣻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⢀⣯⣟⢀⡇
⣇⠹⣟⣾⣻⣿⣿⢾⡽⣿⣿⣿⣿⣿⣆⢹⣶⣿⣻⣷⣯⣟⣿⣿⣽⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⢀⡿⡇⢸⡇
⣿⣆⠹⣷⡻⣽⣿⣯⢿⣽⣻⣿⣿⣿⣿⣆⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠛⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠇⢸⣿⠇⣼⡇
⡙⠾⣆⠹⣿⣦⠛⣿⢯⣷⢿⡽⣿⣿⣿⣿⣆⠻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠃⠎⢸⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠏⢀⣿⣾⣣⡿⡇
⣿⣷⡌⢦⠙⣿⣿⣌⠻⣽⢯⣿⣽⣻⣿⣿⣿⣧⠩⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡏⢰⢣⠘⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠃⢀⢀⢿⣞⣷⢿⡇
⣿⣽⣆⠹⣧⠘⣿⣿⡷⣌⠙⢷⣯⡷⣟⣿⣿⣿⣷⡀⡹⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⣈⠃⣸⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠟⢀⣴⡧⢀⠸⣿⡽⣿⢀
⢻⣽⣿⡄⢻⣷⡈⢿⣿⣿⢧⢀⠙⢿⣻⡾⣽⣻⣿⣿⣄⠌⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠛⢁⣰⣾⣟⡿⢀⡄⢿⣟⣿⢀
⡄⢿⣿⣷⢀⠹⣟⣆⠻⣿⣿⣆⢀⣀⠉⠻⣿⡽⣯⣿⣿⣷⣈⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠋⢀⣠⠘⣯⣷⣿⡟⢀⢆⠸⣿⡟⢸
⣷⡈⢿⣿⣇⢱⡘⢿⣷⣬⣙⠿⣧⠘⣆⢀⠈⠻⣷⣟⣾⢿⣿⣆⠹⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠋⣠⡞⢡⣿⢀⣿⣿⣿⠇⡄⢸⡄⢻⡇⣼
⣿⣷⡈⢿⣿⡆⢣⡀⠙⢾⣟⣿⣿⣷⡈⠂⠘⣦⡈⠿⣯⣿⢾⣿⣆⠙⠻⠿⠿⠿⠿⡿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠿⠛⢋⣠⣾⡟⢠⣿⣿⢀⣿⣿⡟⢠⣿⢈⣧⠘⢠⣿
⣿⣿⣿⣄⠻⣿⡄⢳⡄⢆⡙⠾⣽⣿⣿⣆⡀⢹⡷⣄⠙⢿⣿⡾⣿⣆⢀⡀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⣀⣠⣴⡿⣯⠏⣠⣿⣿⡏⢸⣿⡿⢁⣿⣿⢀⣿⠆⢸⣿
⣿⣿⣿⣿⣦⡙⣿⣆⢻⡌⢿⣶⢤⣉⣙⣿⣷⡀⠙⠽⠷⠄⠹⣿⣟⣿⣆⢙⣋⣤⣤⣤⣄⣀⢀⢀⢀⢀⣾⣿⣟⡷⣯⡿⢃⣼⣿⣿⣿⠇⣼⡟⣡⣿⣿⣿⢀⡿⢠⠈⣿
⣿⣿⣿⣿⣿⣷⣮⣿⣿⣿⡌⠁⢤⣤⣤⣤⣬⣭⣴⣶⣶⣶⣆⠈⢻⣿⣿⣆⢻⣿⣿⣿⣿⣿⣿⣷⣶⣤⣌⣉⡘⠛⠻⠶⣿⣿⣿⣿⡟⣰⣫⣴⣿⣿⣿⣿⠄⣷⣿⣿⣿
*/

import javax.sound.midi.Soundbank;
import java.io.*;
import java.util.*;

public class D {

    /**
     * TODO 提交的时候一定要设置为 true
     */
    boolean submitFlag = true;

    private void solve(int n, int k, int[] a) {
        for (int i = 0; i < a.length; i++) {
            a[i] = a[i] % k;
        }
        Arrays.sort(a);
        int ansI = 0;
        int ans = 0;
        int i = 0;

        int temp = 0;
        int tempI = 0;
        for (i = 0; i < a.length; i++) {
            if (a[i] != 0) {
                break;
            }
        }

        for (; i < a.length; i++) {
            temp = a[i];
            tempI = 0;
            while (i < a.length && a[i] == temp) {
                tempI++;
                i++;
            }
            i--;
            if (tempI > ansI) {
                ansI = tempI;
                ans = temp;
            }
        }
        if (ansI > 0) {
            // 补值
            int gg = k - ans + 1;
            System.out.println((ansI - 1) * k + gg);
        } else {
            System.out.println(0);
        }

    }

    private void run() throws IOException {
        //TODO 从这里开始读入题目输入
        int numberOfTestcases = nextInt();

        for (int t = 0; t < numberOfTestcases; t++) {
            int n = nextInt();
            int k = nextInt();
            int[] a = new int[n];
            for (int i = 0; i < n; i++) {
                a[i] = nextInt();

            }
            solve(n, k, a);
        }

    }

//    main以及输入输出========================================================================

    public static void main(String[] args) throws IOException {
        D solution = new D();
        solution.setReader();
        solution.run();
        solution.reader.close();
    }

    /**
     * 注意不同题目这里路径要设一下
     *
     * @throws IOException
     */
    private void setReader() throws IOException {
        if (submitFlag) {
            reader = new BufferedReader(new InputStreamReader(System.in));
        } else {
            String path = this.getClass().getResource("").getPath();
            File file = new File(path);
            while (!file.getName().equals("target")) {
                file = file.getParentFile();
            }
            String moduleName = file.getParentFile().getName();
            String projectPath = System.getProperty("user.dir");
            String modulePath = projectPath + "/" + moduleName + "/src/main/java/";
            String className = this.getClass().getName().replace(".", "\\");
            reader = new BufferedReader(new FileReader(modulePath + className + "input.txt"));
        }
    }

    BufferedReader reader;
    StringTokenizer tokenizer;

    int nextInt() throws IOException {
        return Integer.parseInt(nextToken());
    }

    long nextLong() throws IOException {
        return Long.parseLong(nextToken());
    }

    double nextDouble() throws IOException {
        return Double.parseDouble(nextToken());
    }

    String next() throws IOException {
        return nextToken();
    }

    String nextToken() throws IOException {
        while (tokenizer == null || !tokenizer.hasMoreTokens()) {
            tokenizer = new StringTokenizer(reader.readLine());
        }
        return tokenizer.nextToken();
    }
}


/*   盗图小能手
⣿⣿⣿⣿⣿⣿⡷⣯⢿⣿⣷⣻⢯⣿⡽⣻⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣇⠸⣿⣿⣆⠹⣿⣿⢾⣟⣯⣿⣿⣿⣿⣿⣿⣽⣻⣿⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣻⣽⡿⣿⣎⠙⣿⣞⣷⡌⢻⣟⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⣿⣿⣿⣿⣿⣿⡄⠹⣿⣿⡆⠻⣿⣟⣯⡿⣽⡿⣿⣿⣿⣿⣽⡷⣯⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣟⣷⣿⣿⣿⡀⠹⣟⣾⣟⣆⠹⣯⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡇⢠⡘⣿⣿⡄⠉⢿⣿⣽⡷⣿⣻⣿⣿⣿⣿⡝⣷⣯⢿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣯⢿⣾⢿⣿⡄⢄⠘⢿⣞⡿⣧⡈⢷⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡇⢸⣧⠘⣿⣷⠈⣦⠙⢿⣽⣷⣻⣽⣿⣿⣿⣿⣌⢿⣯⢿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣟⣯⣿⢿⣿⡆⢸⡷⡈⢻⡽⣷⡷⡄⠻⣽⣿⣿⡿⣿⣿⣿⣿⣿⣿⣷⣿⣿⣿⣿⣏⢰⣯⢷⠈⣿⡆⢹⢷⡌⠻⡾⢋⣱⣯⣿⣿⣿⣿⡆⢻⡿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⡎⣿⢾⡿⣿⡆⢸⣽⢻⣄⠹⣷⣟⣿⣄⠹⣟⣿⣿⣟⣿⣿⣿⣿⣿⣿⣽⣿⣿⣿⡇⢸⣯⣟⣧⠘⣷⠈⡯⠛⢀⡐⢾⣟⣷⣻⣿⣿⣿⡿⡌⢿⣻⣿⣿
⣿⣿⣿⣿⣿⣿⣧⢸⡿⣟⣿⡇⢸⣯⣟⣮⢧⡈⢿⣞⡿⣦⠘⠏⣹⣿⣽⢿⣿⣿⣿⣿⣯⣿⣿⣿⡇⢸⣿⣿⣾⡆⠹⢀⣠⣾⣟⣷⡈⢿⣞⣯⢿⣿⣿⣿⢷⠘⣯⣿⣿
⣿⣿⣿⣿⣿⣿⣿⡈⣿⢿⣽⡇⠘⠛⠛⠛⠓⠓⠈⠛⠛⠟⠇⢀⢿⣻⣿⣯⢿⣿⣿⣿⣷⢿⣿⣿⠁⣾⣿⣿⣿⣧⡄⠇⣹⣿⣾⣯⣿⡄⠻⣽⣯⢿⣻⣿⣿⡇⢹⣾⣿
⣿⣿⣿⣿⣿⣿⣿⡇⢹⣿⡽⡇⢸⣿⣿⣿⣿⣿⣞⣆⠰⣶⣶⡄⢀⢻⡿⣯⣿⡽⣿⣿⣿⢯⣟⡿⢀⣿⣿⣿⣿⣿⣧⠐⣸⣿⣿⣷⣿⣿⣆⠹⣯⣿⣻⣿⣿⣿⢀⣿⢿
⣿⣿⣿⣿⣿⣿⣿⣿⠘⣯⡿⡇⢸⣿⣿⣿⣿⣿⣿⣿⣧⡈⢿⣳⠘⡄⠻⣿⢾⣽⣟⡿⣿⢯⣿⡇⢸⣿⣿⣿⣿⣿⣿⡀⢾⣿⣿⣿⣿⣿⣿⣆⠹⣾⣷⣻⣿⡿⡇⢸⣿
⣿⣿⣿⣿⣿⣿⣿⣿⡇⢹⣿⠇⢸⣿⣿⣿⣿⣿⣿⣿⣿⣷⣄⠻⡇⢹⣆⠹⣟⣾⣽⣻⣟⣿⣽⠁⣾⣿⣿⣿⣿⣿⣿⣇⣿⣿⠿⠛⠛⠉⠙⠋⢀⠁⢘⣯⣿⣿⣧⠘⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⡈⣿⡃⢼⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣦⡙⠌⣿⣆⠘⣿⣞⡿⣞⡿⡞⢠⣿⣿⣿⣿⣿⡿⠛⠉⠁⢀⣀⣠⣤⣤⣶⣶⣶⡆⢻⣽⣞⡿⣷⠈⣿
⣿⣿⣿⣿⣿⣿⣿⣿⡿⠃⠘⠁⠉⠉⠉⠉⠉⠉⠉⠉⠉⠙⠛⠛⢿⣄⢻⣿⣧⠘⢯⣟⡿⣽⠁⣾⣿⣿⣿⣿⣿⡃⢀⢀⠘⠛⠿⢿⣻⣟⣯⣽⣻⣵⡀⢿⣯⣟⣿⢀⣿
⣿⣿⣿⣟⣿⣿⣿⣿⣶⣶⡆⢀⣿⣾⣿⣾⣷⣿⣶⠿⠚⠉⢀⢀⣤⣿⣷⣿⣿⣷⡈⢿⣻⢃⣼⣿⣿⣿⣿⣻⣿⣿⣿⡶⣦⣤⣄⣀⡀⠉⠛⠛⠷⣯⣳⠈⣾⡽⣾⢀⣿
⣿⢿⣿⣿⣻⣿⣿⣿⣿⣿⡿⠐⣿⣿⣿⣿⠿⠋⠁⢀⢀⣤⣾⣿⣿⣿⣿⣿⣿⣿⣿⣌⣥⣾⡿⣿⣿⣷⣿⣿⢿⣷⣿⣿⣟⣾⣽⣳⢯⣟⣶⣦⣤⡾⣟⣦⠘⣿⢾⡁⢺
⣿⣻⣿⣿⡷⣿⣿⣿⣿⣿⡗⣦⠸⡿⠋⠁⢀⢀⣠⣴⢿⣿⣽⣻⢽⣾⣟⣷⣿⣟⣿⣿⣿⣳⠿⣵⣧⣼⣿⣿⣿⣿⣿⣾⣿⣿⣿⣿⣿⣽⣳⣯⣿⣿⣿⣽⢀⢷⣻⠄⠘
⣿⢷⣻⣿⣿⣷⣻⣿⣿⣿⡷⠛⣁⢀⣀⣤⣶⣿⣛⡿⣿⣮⣽⡻⣿⣮⣽⣻⢯⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣯⢀⢸⣿⢀⡆
⠸⣟⣯⣿⣿⣷⢿⣽⣿⣿⣷⣿⣷⣆⠹⣿⣶⣯⠿⣿⣶⣟⣻⢿⣷⣽⣻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⢀⣯⣟⢀⡇
⣇⠹⣟⣾⣻⣿⣿⢾⡽⣿⣿⣿⣿⣿⣆⢹⣶⣿⣻⣷⣯⣟⣿⣿⣽⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⢀⡿⡇⢸⡇
⣿⣆⠹⣷⡻⣽⣿⣯⢿⣽⣻⣿⣿⣿⣿⣆⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠛⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠇⢸⣿⠇⣼⡇
⡙⠾⣆⠹⣿⣦⠛⣿⢯⣷⢿⡽⣿⣿⣿⣿⣆⠻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠃⠎⢸⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠏⢀⣿⣾⣣⡿⡇
⣿⣷⡌⢦⠙⣿⣿⣌⠻⣽⢯⣿⣽⣻⣿⣿⣿⣧⠩⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡏⢰⢣⠘⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠃⢀⢀⢿⣞⣷⢿⡇
⣿⣽⣆⠹⣧⠘⣿⣿⡷⣌⠙⢷⣯⡷⣟⣿⣿⣿⣷⡀⡹⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⣈⠃⣸⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠟⢀⣴⡧⢀⠸⣿⡽⣿⢀
⢻⣽⣿⡄⢻⣷⡈⢿⣿⣿⢧⢀⠙⢿⣻⡾⣽⣻⣿⣿⣄⠌⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠛⢁⣰⣾⣟⡿⢀⡄⢿⣟⣿⢀
⡄⢿⣿⣷⢀⠹⣟⣆⠻⣿⣿⣆⢀⣀⠉⠻⣿⡽⣯⣿⣿⣷⣈⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠋⢀⣠⠘⣯⣷⣿⡟⢀⢆⠸⣿⡟⢸
⣷⡈⢿⣿⣇⢱⡘⢿⣷⣬⣙⠿⣧⠘⣆⢀⠈⠻⣷⣟⣾⢿⣿⣆⠹⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠋⣠⡞⢡⣿⢀⣿⣿⣿⠇⡄⢸⡄⢻⡇⣼
⣿⣷⡈⢿⣿⡆⢣⡀⠙⢾⣟⣿⣿⣷⡈⠂⠘⣦⡈⠿⣯⣿⢾⣿⣆⠙⠻⠿⠿⠿⠿⡿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠿⠛⢋⣠⣾⡟⢠⣿⣿⢀⣿⣿⡟⢠⣿⢈⣧⠘⢠⣿
⣿⣿⣿⣄⠻⣿⡄⢳⡄⢆⡙⠾⣽⣿⣿⣆⡀⢹⡷⣄⠙⢿⣿⡾⣿⣆⢀⡀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⣀⣠⣴⡿⣯⠏⣠⣿⣿⡏⢸⣿⡿⢁⣿⣿⢀⣿⠆⢸⣿
⣿⣿⣿⣿⣦⡙⣿⣆⢻⡌⢿⣶⢤⣉⣙⣿⣷⡀⠙⠽⠷⠄⠹⣿⣟⣿⣆⢙⣋⣤⣤⣤⣄⣀⢀⢀⢀⢀⣾⣿⣟⡷⣯⡿⢃⣼⣿⣿⣿⠇⣼⡟⣡⣿⣿⣿⢀⡿⢠⠈⣿
⣿⣿⣿⣿⣿⣷⣮⣿⣿⣿⡌⠁⢤⣤⣤⣤⣬⣭⣴⣶⣶⣶⣆⠈⢻⣿⣿⣆⢻⣿⣿⣿⣿⣿⣿⣷⣶⣤⣌⣉⡘⠛⠻⠶⣿⣿⣿⣿⡟⣰⣫⣴⣿⣿⣿⣿⠄⣷⣿⣿⣿
*/

import javax.sound.midi.Soundbank;
import java.io.*;
import java.util.*;

public class D {

    /**
     * TODO 提交的时候一定要设置为 true
     */
    boolean submitFlag = true;

    private void solve(int n, int k, int[] a) {
        int mod = 0;
        int index = 0;
        // 余数累计
        int[] num = new int[k];
        for (int i = 0; i < a.length; i++) {
            num[a[i] % k]++;
        }
//        System.out.println(Arrays.toString(num));

        for (int i = 1; i < k; i++) {
            if (num[i] > mod) {
                mod = num[i];
                index = i;
            }
        }

        if (mod > 0) {
            // 补值
            int gg = k - index+1;
            System.out.println((mod - 1) * k + gg);
        } else {
            System.out.println(0);
        }

    }

    private void run() throws IOException {
        //TODO 从这里开始读入题目输入
        int numberOfTestcases = nextInt();

        for (int t = 0; t < numberOfTestcases; t++) {
            int n = nextInt();
            int k = nextInt();
            int[] a = new int[n];
            for (int i = 0; i < n; i++) {
                a[i] = nextInt();
            }
            solve(n, k, a);
        }

    }

//    main以及输入输出========================================================================

    public static void main(String[] args) throws IOException {
        D solution = new D();
        solution.setReader();
        solution.run();
        solution.reader.close();
    }

    /**
     * 注意不同题目这里路径要设一下
     *
     * @throws IOException
     */
    private void setReader() throws IOException {
        if (submitFlag) {
            reader = new BufferedReader(new InputStreamReader(System.in));
        } else {
            String path = this.getClass().getResource("").getPath();
            File file = new File(path);
            while (!file.getName().equals("target")) {
                file = file.getParentFile();
            }
            String moduleName = file.getParentFile().getName();
            String projectPath = System.getProperty("user.dir");
            String modulePath = projectPath + "/" + moduleName + "/src/main/java/";
            String className = this.getClass().getName().replace(".", "\\");
            reader = new BufferedReader(new FileReader(modulePath + className + "input.txt"));
        }
    }

    BufferedReader reader;
    StringTokenizer tokenizer;

    int nextInt() throws IOException {
        return Integer.parseInt(nextToken());
    }

    long nextLong() throws IOException {
        return Long.parseLong(nextToken());
    }

    double nextDouble() throws IOException {
        return Double.parseDouble(nextToken());
    }

    String next() throws IOException {
        return nextToken();
    }

    String nextToken() throws IOException {
        while (tokenizer == null || !tokenizer.hasMoreTokens()) {
            tokenizer = new StringTokenizer(reader.readLine());
        }
        return tokenizer.nextToken();
    }
}


/*   盗图小能手
⣿⣿⣿⣿⣿⣿⡷⣯⢿⣿⣷⣻⢯⣿⡽⣻⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣇⠸⣿⣿⣆⠹⣿⣿⢾⣟⣯⣿⣿⣿⣿⣿⣿⣽⣻⣿⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣻⣽⡿⣿⣎⠙⣿⣞⣷⡌⢻⣟⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⣿⣿⣿⣿⣿⣿⡄⠹⣿⣿⡆⠻⣿⣟⣯⡿⣽⡿⣿⣿⣿⣿⣽⡷⣯⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣟⣷⣿⣿⣿⡀⠹⣟⣾⣟⣆⠹⣯⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡇⢠⡘⣿⣿⡄⠉⢿⣿⣽⡷⣿⣻⣿⣿⣿⣿⡝⣷⣯⢿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣯⢿⣾⢿⣿⡄⢄⠘⢿⣞⡿⣧⡈⢷⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡇⢸⣧⠘⣿⣷⠈⣦⠙⢿⣽⣷⣻⣽⣿⣿⣿⣿⣌⢿⣯⢿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣟⣯⣿⢿⣿⡆⢸⡷⡈⢻⡽⣷⡷⡄⠻⣽⣿⣿⡿⣿⣿⣿⣿⣿⣿⣷⣿⣿⣿⣿⣏⢰⣯⢷⠈⣿⡆⢹⢷⡌⠻⡾⢋⣱⣯⣿⣿⣿⣿⡆⢻⡿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⡎⣿⢾⡿⣿⡆⢸⣽⢻⣄⠹⣷⣟⣿⣄⠹⣟⣿⣿⣟⣿⣿⣿⣿⣿⣿⣽⣿⣿⣿⡇⢸⣯⣟⣧⠘⣷⠈⡯⠛⢀⡐⢾⣟⣷⣻⣿⣿⣿⡿⡌⢿⣻⣿⣿
⣿⣿⣿⣿⣿⣿⣧⢸⡿⣟⣿⡇⢸⣯⣟⣮⢧⡈⢿⣞⡿⣦⠘⠏⣹⣿⣽⢿⣿⣿⣿⣿⣯⣿⣿⣿⡇⢸⣿⣿⣾⡆⠹⢀⣠⣾⣟⣷⡈⢿⣞⣯⢿⣿⣿⣿⢷⠘⣯⣿⣿
⣿⣿⣿⣿⣿⣿⣿⡈⣿⢿⣽⡇⠘⠛⠛⠛⠓⠓⠈⠛⠛⠟⠇⢀⢿⣻⣿⣯⢿⣿⣿⣿⣷⢿⣿⣿⠁⣾⣿⣿⣿⣧⡄⠇⣹⣿⣾⣯⣿⡄⠻⣽⣯⢿⣻⣿⣿⡇⢹⣾⣿
⣿⣿⣿⣿⣿⣿⣿⡇⢹⣿⡽⡇⢸⣿⣿⣿⣿⣿⣞⣆⠰⣶⣶⡄⢀⢻⡿⣯⣿⡽⣿⣿⣿⢯⣟⡿⢀⣿⣿⣿⣿⣿⣧⠐⣸⣿⣿⣷⣿⣿⣆⠹⣯⣿⣻⣿⣿⣿⢀⣿⢿
⣿⣿⣿⣿⣿⣿⣿⣿⠘⣯⡿⡇⢸⣿⣿⣿⣿⣿⣿⣿⣧⡈⢿⣳⠘⡄⠻⣿⢾⣽⣟⡿⣿⢯⣿⡇⢸⣿⣿⣿⣿⣿⣿⡀⢾⣿⣿⣿⣿⣿⣿⣆⠹⣾⣷⣻⣿⡿⡇⢸⣿
⣿⣿⣿⣿⣿⣿⣿⣿⡇⢹⣿⠇⢸⣿⣿⣿⣿⣿⣿⣿⣿⣷⣄⠻⡇⢹⣆⠹⣟⣾⣽⣻⣟⣿⣽⠁⣾⣿⣿⣿⣿⣿⣿⣇⣿⣿⠿⠛⠛⠉⠙⠋⢀⠁⢘⣯⣿⣿⣧⠘⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⡈⣿⡃⢼⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣦⡙⠌⣿⣆⠘⣿⣞⡿⣞⡿⡞⢠⣿⣿⣿⣿⣿⡿⠛⠉⠁⢀⣀⣠⣤⣤⣶⣶⣶⡆⢻⣽⣞⡿⣷⠈⣿
⣿⣿⣿⣿⣿⣿⣿⣿⡿⠃⠘⠁⠉⠉⠉⠉⠉⠉⠉⠉⠉⠙⠛⠛⢿⣄⢻⣿⣧⠘⢯⣟⡿⣽⠁⣾⣿⣿⣿⣿⣿⡃⢀⢀⠘⠛⠿⢿⣻⣟⣯⣽⣻⣵⡀⢿⣯⣟⣿⢀⣿
⣿⣿⣿⣟⣿⣿⣿⣿⣶⣶⡆⢀⣿⣾⣿⣾⣷⣿⣶⠿⠚⠉⢀⢀⣤⣿⣷⣿⣿⣷⡈⢿⣻⢃⣼⣿⣿⣿⣿⣻⣿⣿⣿⡶⣦⣤⣄⣀⡀⠉⠛⠛⠷⣯⣳⠈⣾⡽⣾⢀⣿
⣿⢿⣿⣿⣻⣿⣿⣿⣿⣿⡿⠐⣿⣿⣿⣿⠿⠋⠁⢀⢀⣤⣾⣿⣿⣿⣿⣿⣿⣿⣿⣌⣥⣾⡿⣿⣿⣷⣿⣿⢿⣷⣿⣿⣟⣾⣽⣳⢯⣟⣶⣦⣤⡾⣟⣦⠘⣿⢾⡁⢺
⣿⣻⣿⣿⡷⣿⣿⣿⣿⣿⡗⣦⠸⡿⠋⠁⢀⢀⣠⣴⢿⣿⣽⣻⢽⣾⣟⣷⣿⣟⣿⣿⣿⣳⠿⣵⣧⣼⣿⣿⣿⣿⣿⣾⣿⣿⣿⣿⣿⣽⣳⣯⣿⣿⣿⣽⢀⢷⣻⠄⠘
⣿⢷⣻⣿⣿⣷⣻⣿⣿⣿⡷⠛⣁⢀⣀⣤⣶⣿⣛⡿⣿⣮⣽⡻⣿⣮⣽⣻⢯⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣯⢀⢸⣿⢀⡆
⠸⣟⣯⣿⣿⣷⢿⣽⣿⣿⣷⣿⣷⣆⠹⣿⣶⣯⠿⣿⣶⣟⣻⢿⣷⣽⣻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⢀⣯⣟⢀⡇
⣇⠹⣟⣾⣻⣿⣿⢾⡽⣿⣿⣿⣿⣿⣆⢹⣶⣿⣻⣷⣯⣟⣿⣿⣽⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⢀⡿⡇⢸⡇
⣿⣆⠹⣷⡻⣽⣿⣯⢿⣽⣻⣿⣿⣿⣿⣆⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠛⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠇⢸⣿⠇⣼⡇
⡙⠾⣆⠹⣿⣦⠛⣿⢯⣷⢿⡽⣿⣿⣿⣿⣆⠻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠃⠎⢸⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠏⢀⣿⣾⣣⡿⡇
⣿⣷⡌⢦⠙⣿⣿⣌⠻⣽⢯⣿⣽⣻⣿⣿⣿⣧⠩⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡏⢰⢣⠘⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠃⢀⢀⢿⣞⣷⢿⡇
⣿⣽⣆⠹⣧⠘⣿⣿⡷⣌⠙⢷⣯⡷⣟⣿⣿⣿⣷⡀⡹⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⣈⠃⣸⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠟⢀⣴⡧⢀⠸⣿⡽⣿⢀
⢻⣽⣿⡄⢻⣷⡈⢿⣿⣿⢧⢀⠙⢿⣻⡾⣽⣻⣿⣿⣄⠌⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠛⢁⣰⣾⣟⡿⢀⡄⢿⣟⣿⢀
⡄⢿⣿⣷⢀⠹⣟⣆⠻⣿⣿⣆⢀⣀⠉⠻⣿⡽⣯⣿⣿⣷⣈⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠋⢀⣠⠘⣯⣷⣿⡟⢀⢆⠸⣿⡟⢸
⣷⡈⢿⣿⣇⢱⡘⢿⣷⣬⣙⠿⣧⠘⣆⢀⠈⠻⣷⣟⣾⢿⣿⣆⠹⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠋⣠⡞⢡⣿⢀⣿⣿⣿⠇⡄⢸⡄⢻⡇⣼
⣿⣷⡈⢿⣿⡆⢣⡀⠙⢾⣟⣿⣿⣷⡈⠂⠘⣦⡈⠿⣯⣿⢾⣿⣆⠙⠻⠿⠿⠿⠿⡿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠿⠛⢋⣠⣾⡟⢠⣿⣿⢀⣿⣿⡟⢠⣿⢈⣧⠘⢠⣿
⣿⣿⣿⣄⠻⣿⡄⢳⡄⢆⡙⠾⣽⣿⣿⣆⡀⢹⡷⣄⠙⢿⣿⡾⣿⣆⢀⡀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⣀⣠⣴⡿⣯⠏⣠⣿⣿⡏⢸⣿⡿⢁⣿⣿⢀⣿⠆⢸⣿
⣿⣿⣿⣿⣦⡙⣿⣆⢻⡌⢿⣶⢤⣉⣙⣿⣷⡀⠙⠽⠷⠄⠹⣿⣟⣿⣆⢙⣋⣤⣤⣤⣄⣀⢀⢀⢀⢀⣾⣿⣟⡷⣯⡿⢃⣼⣿⣿⣿⠇⣼⡟⣡⣿⣿⣿⢀⡿⢠⠈⣿
⣿⣿⣿⣿⣿⣷⣮⣿⣿⣿⡌⠁⢤⣤⣤⣤⣬⣭⣴⣶⣶⣶⣆⠈⢻⣿⣿⣆⢻⣿⣿⣿⣿⣿⣿⣷⣶⣤⣌⣉⡘⠛⠻⠶⣿⣿⣿⣿⡟⣰⣫⣴⣿⣿⣿⣿⠄⣷⣿⣿⣿
*/

import javax.sound.midi.Soundbank;
import java.io.*;
import java.util.*;

public class D {

    /**
     * TODO 提交的时候一定要设置为 true
     */
    boolean submitFlag = true;

    private void run() throws IOException {
        //TODO 从这里开始读入题目输入
        int numberOfTestcases = nextInt();

        for (int t = 0; t < numberOfTestcases; t++) {
            int n = nextInt();
            int k = nextInt();
            long ans = -1;
            // 余数累计
            Map<Integer, Long> map = new HashMap<>();
            for (int i = 0; i < n; i++) {
                int data = nextInt();
                int key = data % k;
                if (key != 0) {
                    Long orDefault = map.getOrDefault(key, 0L);
                    orDefault++;
                    map.put(key, orDefault);
                    ans = Math.max(ans, orDefault * k - key);
                }
            }
            System.out.println(ans + 1);
        }
    }

//    main以及输入输出========================================================================

    public static void main(String[] args) throws IOException {
        D solution = new D();
        solution.setReader();
        solution.run();
        solution.reader.close();
    }

    /**
     * 注意不同题目这里路径要设一下
     *
     * @throws IOException
     */
    private void setReader() throws IOException {
        if (submitFlag) {
            reader = new BufferedReader(new InputStreamReader(System.in));
        } else {
            String path = this.getClass().getResource("").getPath();
            File file = new File(path);
            while (!file.getName().equals("target")) {
                file = file.getParentFile();
            }
            String moduleName = file.getParentFile().getName();
            String projectPath = System.getProperty("user.dir");
            String modulePath = projectPath + "/" + moduleName + "/src/main/java/";
            String className = this.getClass().getName().replace(".", "\\");
            reader = new BufferedReader(new FileReader(modulePath + className + "input.txt"));
        }
    }

    BufferedReader reader;
    StringTokenizer tokenizer;

    int nextInt() throws IOException {
        return Integer.parseInt(nextToken());
    }

    long nextLong() throws IOException {
        return Long.parseLong(nextToken());
    }

    double nextDouble() throws IOException {
        return Double.parseDouble(nextToken());
    }

    String next() throws IOException {
        return nextToken();
    }

    String nextToken() throws IOException {
        while (tokenizer == null || !tokenizer.hasMoreTokens()) {
            tokenizer = new StringTokenizer(reader.readLine());
        }
        return tokenizer.nextToken();
    }
}


/*   盗图小能手
⣿⣿⣿⣿⣿⣿⡷⣯⢿⣿⣷⣻⢯⣿⡽⣻⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣇⠸⣿⣿⣆⠹⣿⣿⢾⣟⣯⣿⣿⣿⣿⣿⣿⣽⣻⣿⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣻⣽⡿⣿⣎⠙⣿⣞⣷⡌⢻⣟⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⣿⣿⣿⣿⣿⣿⡄⠹⣿⣿⡆⠻⣿⣟⣯⡿⣽⡿⣿⣿⣿⣿⣽⡷⣯⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣟⣷⣿⣿⣿⡀⠹⣟⣾⣟⣆⠹⣯⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡇⢠⡘⣿⣿⡄⠉⢿⣿⣽⡷⣿⣻⣿⣿⣿⣿⡝⣷⣯⢿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣯⢿⣾⢿⣿⡄⢄⠘⢿⣞⡿⣧⡈⢷⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡇⢸⣧⠘⣿⣷⠈⣦⠙⢿⣽⣷⣻⣽⣿⣿⣿⣿⣌⢿⣯⢿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣟⣯⣿⢿⣿⡆⢸⡷⡈⢻⡽⣷⡷⡄⠻⣽⣿⣿⡿⣿⣿⣿⣿⣿⣿⣷⣿⣿⣿⣿⣏⢰⣯⢷⠈⣿⡆⢹⢷⡌⠻⡾⢋⣱⣯⣿⣿⣿⣿⡆⢻⡿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⡎⣿⢾⡿⣿⡆⢸⣽⢻⣄⠹⣷⣟⣿⣄⠹⣟⣿⣿⣟⣿⣿⣿⣿⣿⣿⣽⣿⣿⣿⡇⢸⣯⣟⣧⠘⣷⠈⡯⠛⢀⡐⢾⣟⣷⣻⣿⣿⣿⡿⡌⢿⣻⣿⣿
⣿⣿⣿⣿⣿⣿⣧⢸⡿⣟⣿⡇⢸⣯⣟⣮⢧⡈⢿⣞⡿⣦⠘⠏⣹⣿⣽⢿⣿⣿⣿⣿⣯⣿⣿⣿⡇⢸⣿⣿⣾⡆⠹⢀⣠⣾⣟⣷⡈⢿⣞⣯⢿⣿⣿⣿⢷⠘⣯⣿⣿
⣿⣿⣿⣿⣿⣿⣿⡈⣿⢿⣽⡇⠘⠛⠛⠛⠓⠓⠈⠛⠛⠟⠇⢀⢿⣻⣿⣯⢿⣿⣿⣿⣷⢿⣿⣿⠁⣾⣿⣿⣿⣧⡄⠇⣹⣿⣾⣯⣿⡄⠻⣽⣯⢿⣻⣿⣿⡇⢹⣾⣿
⣿⣿⣿⣿⣿⣿⣿⡇⢹⣿⡽⡇⢸⣿⣿⣿⣿⣿⣞⣆⠰⣶⣶⡄⢀⢻⡿⣯⣿⡽⣿⣿⣿⢯⣟⡿⢀⣿⣿⣿⣿⣿⣧⠐⣸⣿⣿⣷⣿⣿⣆⠹⣯⣿⣻⣿⣿⣿⢀⣿⢿
⣿⣿⣿⣿⣿⣿⣿⣿⠘⣯⡿⡇⢸⣿⣿⣿⣿⣿⣿⣿⣧⡈⢿⣳⠘⡄⠻⣿⢾⣽⣟⡿⣿⢯⣿⡇⢸⣿⣿⣿⣿⣿⣿⡀⢾⣿⣿⣿⣿⣿⣿⣆⠹⣾⣷⣻⣿⡿⡇⢸⣿
⣿⣿⣿⣿⣿⣿⣿⣿⡇⢹⣿⠇⢸⣿⣿⣿⣿⣿⣿⣿⣿⣷⣄⠻⡇⢹⣆⠹⣟⣾⣽⣻⣟⣿⣽⠁⣾⣿⣿⣿⣿⣿⣿⣇⣿⣿⠿⠛⠛⠉⠙⠋⢀⠁⢘⣯⣿⣿⣧⠘⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⡈⣿⡃⢼⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣦⡙⠌⣿⣆⠘⣿⣞⡿⣞⡿⡞⢠⣿⣿⣿⣿⣿⡿⠛⠉⠁⢀⣀⣠⣤⣤⣶⣶⣶⡆⢻⣽⣞⡿⣷⠈⣿
⣿⣿⣿⣿⣿⣿⣿⣿⡿⠃⠘⠁⠉⠉⠉⠉⠉⠉⠉⠉⠉⠙⠛⠛⢿⣄⢻⣿⣧⠘⢯⣟⡿⣽⠁⣾⣿⣿⣿⣿⣿⡃⢀⢀⠘⠛⠿⢿⣻⣟⣯⣽⣻⣵⡀⢿⣯⣟⣿⢀⣿
⣿⣿⣿⣟⣿⣿⣿⣿⣶⣶⡆⢀⣿⣾⣿⣾⣷⣿⣶⠿⠚⠉⢀⢀⣤⣿⣷⣿⣿⣷⡈⢿⣻⢃⣼⣿⣿⣿⣿⣻⣿⣿⣿⡶⣦⣤⣄⣀⡀⠉⠛⠛⠷⣯⣳⠈⣾⡽⣾⢀⣿
⣿⢿⣿⣿⣻⣿⣿⣿⣿⣿⡿⠐⣿⣿⣿⣿⠿⠋⠁⢀⢀⣤⣾⣿⣿⣿⣿⣿⣿⣿⣿⣌⣥⣾⡿⣿⣿⣷⣿⣿⢿⣷⣿⣿⣟⣾⣽⣳⢯⣟⣶⣦⣤⡾⣟⣦⠘⣿⢾⡁⢺
⣿⣻⣿⣿⡷⣿⣿⣿⣿⣿⡗⣦⠸⡿⠋⠁⢀⢀⣠⣴⢿⣿⣽⣻⢽⣾⣟⣷⣿⣟⣿⣿⣿⣳⠿⣵⣧⣼⣿⣿⣿⣿⣿⣾⣿⣿⣿⣿⣿⣽⣳⣯⣿⣿⣿⣽⢀⢷⣻⠄⠘
⣿⢷⣻⣿⣿⣷⣻⣿⣿⣿⡷⠛⣁⢀⣀⣤⣶⣿⣛⡿⣿⣮⣽⡻⣿⣮⣽⣻⢯⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣯⢀⢸⣿⢀⡆
⠸⣟⣯⣿⣿⣷⢿⣽⣿⣿⣷⣿⣷⣆⠹⣿⣶⣯⠿⣿⣶⣟⣻⢿⣷⣽⣻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⢀⣯⣟⢀⡇
⣇⠹⣟⣾⣻⣿⣿⢾⡽⣿⣿⣿⣿⣿⣆⢹⣶⣿⣻⣷⣯⣟⣿⣿⣽⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⢀⡿⡇⢸⡇
⣿⣆⠹⣷⡻⣽⣿⣯⢿⣽⣻⣿⣿⣿⣿⣆⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠛⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠇⢸⣿⠇⣼⡇
⡙⠾⣆⠹⣿⣦⠛⣿⢯⣷⢿⡽⣿⣿⣿⣿⣆⠻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠃⠎⢸⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠏⢀⣿⣾⣣⡿⡇
⣿⣷⡌⢦⠙⣿⣿⣌⠻⣽⢯⣿⣽⣻⣿⣿⣿⣧⠩⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡏⢰⢣⠘⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠃⢀⢀⢿⣞⣷⢿⡇
⣿⣽⣆⠹⣧⠘⣿⣿⡷⣌⠙⢷⣯⡷⣟⣿⣿⣿⣷⡀⡹⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⣈⠃⣸⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠟⢀⣴⡧⢀⠸⣿⡽⣿⢀
⢻⣽⣿⡄⢻⣷⡈⢿⣿⣿⢧⢀⠙⢿⣻⡾⣽⣻⣿⣿⣄⠌⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠛⢁⣰⣾⣟⡿⢀⡄⢿⣟⣿⢀
⡄⢿⣿⣷⢀⠹⣟⣆⠻⣿⣿⣆⢀⣀⠉⠻⣿⡽⣯⣿⣿⣷⣈⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠋⢀⣠⠘⣯⣷⣿⡟⢀⢆⠸⣿⡟⢸
⣷⡈⢿⣿⣇⢱⡘⢿⣷⣬⣙⠿⣧⠘⣆⢀⠈⠻⣷⣟⣾⢿⣿⣆⠹⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠋⣠⡞⢡⣿⢀⣿⣿⣿⠇⡄⢸⡄⢻⡇⣼
⣿⣷⡈⢿⣿⡆⢣⡀⠙⢾⣟⣿⣿⣷⡈⠂⠘⣦⡈⠿⣯⣿⢾⣿⣆⠙⠻⠿⠿⠿⠿⡿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠿⠛⢋⣠⣾⡟⢠⣿⣿⢀⣿⣿⡟⢠⣿⢈⣧⠘⢠⣿
⣿⣿⣿⣄⠻⣿⡄⢳⡄⢆⡙⠾⣽⣿⣿⣆⡀⢹⡷⣄⠙⢿⣿⡾⣿⣆⢀⡀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⣀⣠⣴⡿⣯⠏⣠⣿⣿⡏⢸⣿⡿⢁⣿⣿⢀⣿⠆⢸⣿
⣿⣿⣿⣿⣦⡙⣿⣆⢻⡌⢿⣶⢤⣉⣙⣿⣷⡀⠙⠽⠷⠄⠹⣿⣟⣿⣆⢙⣋⣤⣤⣤⣄⣀⢀⢀⢀⢀⣾⣿⣟⡷⣯⡿⢃⣼⣿⣿⣿⠇⣼⡟⣡⣿⣿⣿⢀⡿⢠⠈⣿
⣿⣿⣿⣿⣿⣷⣮⣿⣿⣿⡌⠁⢤⣤⣤⣤⣬⣭⣴⣶⣶⣶⣆⠈⢻⣿⣿⣆⢻⣿⣿⣿⣿⣿⣿⣷⣶⣤⣌⣉⡘⠛⠻⠶⣿⣿⣿⣿⡟⣰⣫⣴⣿⣿⣿⣿⠄⣷⣿⣿⣿
*/

import javax.sound.midi.Soundbank;
import java.io.*;
import java.util.*;

public class D {

    /**
     * TODO 提交的时候一定要设置为 true
     */
    boolean submitFlag = true;

    private void solve(int n, int k, int[] a) {
        for (int i = 0; i < a.length; i++) {
            a[i] = a[i] % k;
        }
        Arrays.sort(a);
        int ansI = 0;
        int ans = 0;
        int i = 0;

        int temp = 0;
        int tempI = 0;
        for (i = 0; i < a.length; i++) {
            if (a[i] != 0) {
                break;
            }
        }

        for (; i < a.length; i++) {
            temp = a[i];
            tempI = 0;
            while (i < a.length && a[i] == temp) {
                tempI++;
                i++;
            }
            if (tempI > ansI) {
                ansI = tempI;
                ans = temp;
            }
            if (i < a.length) {
                i--;
            }
        }
        if (ansI > 0) {
            // 补值
            int gg = k - ans + 1;
            System.out.println((ansI - 1) * k + gg);
        } else {
            System.out.println(0);
        }

    }

    private void run() throws IOException {
        //TODO 从这里开始读入题目输入
        int numberOfTestcases = nextInt();

        for (int t = 0; t < numberOfTestcases; t++) {
            int n = nextInt();
            int k = nextInt();
            int[] a = new int[n];
            for (int i = 0; i < n; i++) {
                a[i] = nextInt();

            }
            solve(n, k, a);
        }

    }

//    main以及输入输出========================================================================

    public static void main(String[] args) throws IOException {
        D solution = new D();
        solution.setReader();
        solution.run();
        solution.reader.close();
    }

    /**
     * 注意不同题目这里路径要设一下
     *
     * @throws IOException
     */
    private void setReader() throws IOException {
        if (submitFlag) {
            reader = new BufferedReader(new InputStreamReader(System.in));
        } else {
            String path = this.getClass().getResource("").getPath();
            File file = new File(path);
            while (!file.getName().equals("target")) {
                file = file.getParentFile();
            }
            String moduleName = file.getParentFile().getName();
            String projectPath = System.getProperty("user.dir");
            String modulePath = projectPath + "/" + moduleName + "/src/main/java/";
            String className = this.getClass().getName().replace(".", "\\");
            reader = new BufferedReader(new FileReader(modulePath + className + "input.txt"));
        }
    }

    BufferedReader reader;
    StringTokenizer tokenizer;

    int nextInt() throws IOException {
        return Integer.parseInt(nextToken());
    }

    long nextLong() throws IOException {
        return Long.parseLong(nextToken());
    }

    double nextDouble() throws IOException {
        return Double.parseDouble(nextToken());
    }

    String next() throws IOException {
        return nextToken();
    }

    String nextToken() throws IOException {
        while (tokenizer == null || !tokenizer.hasMoreTokens()) {
            tokenizer = new StringTokenizer(reader.readLine());
        }
        return tokenizer.nextToken();
    }
}


/*   盗图小能手
⣿⣿⣿⣿⣿⣿⡷⣯⢿⣿⣷⣻⢯⣿⡽⣻⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣇⠸⣿⣿⣆⠹⣿⣿⢾⣟⣯⣿⣿⣿⣿⣿⣿⣽⣻⣿⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣻⣽⡿⣿⣎⠙⣿⣞⣷⡌⢻⣟⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⣿⣿⣿⣿⣿⣿⡄⠹⣿⣿⡆⠻⣿⣟⣯⡿⣽⡿⣿⣿⣿⣿⣽⡷⣯⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣟⣷⣿⣿⣿⡀⠹⣟⣾⣟⣆⠹⣯⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡇⢠⡘⣿⣿⡄⠉⢿⣿⣽⡷⣿⣻⣿⣿⣿⣿⡝⣷⣯⢿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣯⢿⣾⢿⣿⡄⢄⠘⢿⣞⡿⣧⡈⢷⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡇⢸⣧⠘⣿⣷⠈⣦⠙⢿⣽⣷⣻⣽⣿⣿⣿⣿⣌⢿⣯⢿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣟⣯⣿⢿⣿⡆⢸⡷⡈⢻⡽⣷⡷⡄⠻⣽⣿⣿⡿⣿⣿⣿⣿⣿⣿⣷⣿⣿⣿⣿⣏⢰⣯⢷⠈⣿⡆⢹⢷⡌⠻⡾⢋⣱⣯⣿⣿⣿⣿⡆⢻⡿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⡎⣿⢾⡿⣿⡆⢸⣽⢻⣄⠹⣷⣟⣿⣄⠹⣟⣿⣿⣟⣿⣿⣿⣿⣿⣿⣽⣿⣿⣿⡇⢸⣯⣟⣧⠘⣷⠈⡯⠛⢀⡐⢾⣟⣷⣻⣿⣿⣿⡿⡌⢿⣻⣿⣿
⣿⣿⣿⣿⣿⣿⣧⢸⡿⣟⣿⡇⢸⣯⣟⣮⢧⡈⢿⣞⡿⣦⠘⠏⣹⣿⣽⢿⣿⣿⣿⣿⣯⣿⣿⣿⡇⢸⣿⣿⣾⡆⠹⢀⣠⣾⣟⣷⡈⢿⣞⣯⢿⣿⣿⣿⢷⠘⣯⣿⣿
⣿⣿⣿⣿⣿⣿⣿⡈⣿⢿⣽⡇⠘⠛⠛⠛⠓⠓⠈⠛⠛⠟⠇⢀⢿⣻⣿⣯⢿⣿⣿⣿⣷⢿⣿⣿⠁⣾⣿⣿⣿⣧⡄⠇⣹⣿⣾⣯⣿⡄⠻⣽⣯⢿⣻⣿⣿⡇⢹⣾⣿
⣿⣿⣿⣿⣿⣿⣿⡇⢹⣿⡽⡇⢸⣿⣿⣿⣿⣿⣞⣆⠰⣶⣶⡄⢀⢻⡿⣯⣿⡽⣿⣿⣿⢯⣟⡿⢀⣿⣿⣿⣿⣿⣧⠐⣸⣿⣿⣷⣿⣿⣆⠹⣯⣿⣻⣿⣿⣿⢀⣿⢿
⣿⣿⣿⣿⣿⣿⣿⣿⠘⣯⡿⡇⢸⣿⣿⣿⣿⣿⣿⣿⣧⡈⢿⣳⠘⡄⠻⣿⢾⣽⣟⡿⣿⢯⣿⡇⢸⣿⣿⣿⣿⣿⣿⡀⢾⣿⣿⣿⣿⣿⣿⣆⠹⣾⣷⣻⣿⡿⡇⢸⣿
⣿⣿⣿⣿⣿⣿⣿⣿⡇⢹⣿⠇⢸⣿⣿⣿⣿⣿⣿⣿⣿⣷⣄⠻⡇⢹⣆⠹⣟⣾⣽⣻⣟⣿⣽⠁⣾⣿⣿⣿⣿⣿⣿⣇⣿⣿⠿⠛⠛⠉⠙⠋⢀⠁⢘⣯⣿⣿⣧⠘⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⡈⣿⡃⢼⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣦⡙⠌⣿⣆⠘⣿⣞⡿⣞⡿⡞⢠⣿⣿⣿⣿⣿⡿⠛⠉⠁⢀⣀⣠⣤⣤⣶⣶⣶⡆⢻⣽⣞⡿⣷⠈⣿
⣿⣿⣿⣿⣿⣿⣿⣿⡿⠃⠘⠁⠉⠉⠉⠉⠉⠉⠉⠉⠉⠙⠛⠛⢿⣄⢻⣿⣧⠘⢯⣟⡿⣽⠁⣾⣿⣿⣿⣿⣿⡃⢀⢀⠘⠛⠿⢿⣻⣟⣯⣽⣻⣵⡀⢿⣯⣟⣿⢀⣿
⣿⣿⣿⣟⣿⣿⣿⣿⣶⣶⡆⢀⣿⣾⣿⣾⣷⣿⣶⠿⠚⠉⢀⢀⣤⣿⣷⣿⣿⣷⡈⢿⣻⢃⣼⣿⣿⣿⣿⣻⣿⣿⣿⡶⣦⣤⣄⣀⡀⠉⠛⠛⠷⣯⣳⠈⣾⡽⣾⢀⣿
⣿⢿⣿⣿⣻⣿⣿⣿⣿⣿⡿⠐⣿⣿⣿⣿⠿⠋⠁⢀⢀⣤⣾⣿⣿⣿⣿⣿⣿⣿⣿⣌⣥⣾⡿⣿⣿⣷⣿⣿⢿⣷⣿⣿⣟⣾⣽⣳⢯⣟⣶⣦⣤⡾⣟⣦⠘⣿⢾⡁⢺
⣿⣻⣿⣿⡷⣿⣿⣿⣿⣿⡗⣦⠸⡿⠋⠁⢀⢀⣠⣴⢿⣿⣽⣻⢽⣾⣟⣷⣿⣟⣿⣿⣿⣳⠿⣵⣧⣼⣿⣿⣿⣿⣿⣾⣿⣿⣿⣿⣿⣽⣳⣯⣿⣿⣿⣽⢀⢷⣻⠄⠘
⣿⢷⣻⣿⣿⣷⣻⣿⣿⣿⡷⠛⣁⢀⣀⣤⣶⣿⣛⡿⣿⣮⣽⡻⣿⣮⣽⣻⢯⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣯⢀⢸⣿⢀⡆
⠸⣟⣯⣿⣿⣷⢿⣽⣿⣿⣷⣿⣷⣆⠹⣿⣶⣯⠿⣿⣶⣟⣻⢿⣷⣽⣻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⢀⣯⣟⢀⡇
⣇⠹⣟⣾⣻⣿⣿⢾⡽⣿⣿⣿⣿⣿⣆⢹⣶⣿⣻⣷⣯⣟⣿⣿⣽⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⢀⡿⡇⢸⡇
⣿⣆⠹⣷⡻⣽⣿⣯⢿⣽⣻⣿⣿⣿⣿⣆⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠛⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠇⢸⣿⠇⣼⡇
⡙⠾⣆⠹⣿⣦⠛⣿⢯⣷⢿⡽⣿⣿⣿⣿⣆⠻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠃⠎⢸⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠏⢀⣿⣾⣣⡿⡇
⣿⣷⡌⢦⠙⣿⣿⣌⠻⣽⢯⣿⣽⣻⣿⣿⣿⣧⠩⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡏⢰⢣⠘⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠃⢀⢀⢿⣞⣷⢿⡇
⣿⣽⣆⠹⣧⠘⣿⣿⡷⣌⠙⢷⣯⡷⣟⣿⣿⣿⣷⡀⡹⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⣈⠃⣸⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠟⢀⣴⡧⢀⠸⣿⡽⣿⢀
⢻⣽⣿⡄⢻⣷⡈⢿⣿⣿⢧⢀⠙⢿⣻⡾⣽⣻⣿⣿⣄⠌⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠛⢁⣰⣾⣟⡿⢀⡄⢿⣟⣿⢀
⡄⢿⣿⣷⢀⠹⣟⣆⠻⣿⣿⣆⢀⣀⠉⠻⣿⡽⣯⣿⣿⣷⣈⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠋⢀⣠⠘⣯⣷⣿⡟⢀⢆⠸⣿⡟⢸
⣷⡈⢿⣿⣇⢱⡘⢿⣷⣬⣙⠿⣧⠘⣆⢀⠈⠻⣷⣟⣾⢿⣿⣆⠹⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠋⣠⡞⢡⣿⢀⣿⣿⣿⠇⡄⢸⡄⢻⡇⣼
⣿⣷⡈⢿⣿⡆⢣⡀⠙⢾⣟⣿⣿⣷⡈⠂⠘⣦⡈⠿⣯⣿⢾⣿⣆⠙⠻⠿⠿⠿⠿⡿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠿⠛⢋⣠⣾⡟⢠⣿⣿⢀⣿⣿⡟⢠⣿⢈⣧⠘⢠⣿
⣿⣿⣿⣄⠻⣿⡄⢳⡄⢆⡙⠾⣽⣿⣿⣆⡀⢹⡷⣄⠙⢿⣿⡾⣿⣆⢀⡀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⣀⣠⣴⡿⣯⠏⣠⣿⣿⡏⢸⣿⡿⢁⣿⣿⢀⣿⠆⢸⣿
⣿⣿⣿⣿⣦⡙⣿⣆⢻⡌⢿⣶⢤⣉⣙⣿⣷⡀⠙⠽⠷⠄⠹⣿⣟⣿⣆⢙⣋⣤⣤⣤⣄⣀⢀⢀⢀⢀⣾⣿⣟⡷⣯⡿⢃⣼⣿⣿⣿⠇⣼⡟⣡⣿⣿⣿⢀⡿⢠⠈⣿
⣿⣿⣿⣿⣿⣷⣮⣿⣿⣿⡌⠁⢤⣤⣤⣤⣬⣭⣴⣶⣶⣶⣆⠈⢻⣿⣿⣆⢻⣿⣿⣿⣿⣿⣿⣷⣶⣤⣌⣉⡘⠛⠻⠶⣿⣿⣿⣿⡟⣰⣫⣴⣿⣿⣿⣿⠄⣷⣿⣿⣿
*/

import javax.sound.midi.Soundbank;
import java.io.*;
import java.util.*;

public class D {

    /**
     * TODO 提交的时候一定要设置为 true
     */
    boolean submitFlag = true;

    private void run() throws IOException {
        //TODO 从这里开始读入题目输入
        int numberOfTestcases = nextInt();

        for (int t = 0; t < numberOfTestcases; t++) {
            int n = nextInt();
            int k = nextInt();
            int ans = -1;
            // 余数累计
            Map<Integer, Integer> map = new HashMap<>();
            for (int i = 0; i < n; i++) {
                int data = nextInt();
                int key = data % k;
                if (key != 0) {
                    Integer orDefault = map.getOrDefault(key, 0);
                    orDefault++;
                    map.put(key, orDefault);
                    ans = Math.max(ans, orDefault * k - key);
                }
            }
            System.out.println(ans + 1);
        }
    }

//    main以及输入输出========================================================================

    public static void main(String[] args) throws IOException {
        D solution = new D();
        solution.setReader();
        solution.run();
        solution.reader.close();
    }

    /**
     * 注意不同题目这里路径要设一下
     *
     * @throws IOException
     */
    private void setReader() throws IOException {
        if (submitFlag) {
            reader = new BufferedReader(new InputStreamReader(System.in));
        } else {
            String path = this.getClass().getResource("").getPath();
            File file = new File(path);
            while (!file.getName().equals("target")) {
                file = file.getParentFile();
            }
            String moduleName = file.getParentFile().getName();
            String projectPath = System.getProperty("user.dir");
            String modulePath = projectPath + "/" + moduleName + "/src/main/java/";
            String className = this.getClass().getName().replace(".", "\\");
            reader = new BufferedReader(new FileReader(modulePath + className + "input.txt"));
        }
    }

    BufferedReader reader;
    StringTokenizer tokenizer;

    int nextInt() throws IOException {
        return Integer.parseInt(nextToken());
    }

    long nextLong() throws IOException {
        return Long.parseLong(nextToken());
    }

    double nextDouble() throws IOException {
        return Double.parseDouble(nextToken());
    }

    String next() throws IOException {
        return nextToken();
    }

    String nextToken() throws IOException {
        while (tokenizer == null || !tokenizer.hasMoreTokens()) {
            tokenizer = new StringTokenizer(reader.readLine());
        }
        return tokenizer.nextToken();
    }
}


/*   盗图小能手
⣿⣿⣿⣿⣿⣿⡷⣯⢿⣿⣷⣻⢯⣿⡽⣻⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣇⠸⣿⣿⣆⠹⣿⣿⢾⣟⣯⣿⣿⣿⣿⣿⣿⣽⣻⣿⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣻⣽⡿⣿⣎⠙⣿⣞⣷⡌⢻⣟⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⣿⣿⣿⣿⣿⣿⡄⠹⣿⣿⡆⠻⣿⣟⣯⡿⣽⡿⣿⣿⣿⣿⣽⡷⣯⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣟⣷⣿⣿⣿⡀⠹⣟⣾⣟⣆⠹⣯⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡇⢠⡘⣿⣿⡄⠉⢿⣿⣽⡷⣿⣻⣿⣿⣿⣿⡝⣷⣯⢿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣯⢿⣾⢿⣿⡄⢄⠘⢿⣞⡿⣧⡈⢷⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡇⢸⣧⠘⣿⣷⠈⣦⠙⢿⣽⣷⣻⣽⣿⣿⣿⣿⣌⢿⣯⢿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣟⣯⣿⢿⣿⡆⢸⡷⡈⢻⡽⣷⡷⡄⠻⣽⣿⣿⡿⣿⣿⣿⣿⣿⣿⣷⣿⣿⣿⣿⣏⢰⣯⢷⠈⣿⡆⢹⢷⡌⠻⡾⢋⣱⣯⣿⣿⣿⣿⡆⢻⡿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⡎⣿⢾⡿⣿⡆⢸⣽⢻⣄⠹⣷⣟⣿⣄⠹⣟⣿⣿⣟⣿⣿⣿⣿⣿⣿⣽⣿⣿⣿⡇⢸⣯⣟⣧⠘⣷⠈⡯⠛⢀⡐⢾⣟⣷⣻⣿⣿⣿⡿⡌⢿⣻⣿⣿
⣿⣿⣿⣿⣿⣿⣧⢸⡿⣟⣿⡇⢸⣯⣟⣮⢧⡈⢿⣞⡿⣦⠘⠏⣹⣿⣽⢿⣿⣿⣿⣿⣯⣿⣿⣿⡇⢸⣿⣿⣾⡆⠹⢀⣠⣾⣟⣷⡈⢿⣞⣯⢿⣿⣿⣿⢷⠘⣯⣿⣿
⣿⣿⣿⣿⣿⣿⣿⡈⣿⢿⣽⡇⠘⠛⠛⠛⠓⠓⠈⠛⠛⠟⠇⢀⢿⣻⣿⣯⢿⣿⣿⣿⣷⢿⣿⣿⠁⣾⣿⣿⣿⣧⡄⠇⣹⣿⣾⣯⣿⡄⠻⣽⣯⢿⣻⣿⣿⡇⢹⣾⣿
⣿⣿⣿⣿⣿⣿⣿⡇⢹⣿⡽⡇⢸⣿⣿⣿⣿⣿⣞⣆⠰⣶⣶⡄⢀⢻⡿⣯⣿⡽⣿⣿⣿⢯⣟⡿⢀⣿⣿⣿⣿⣿⣧⠐⣸⣿⣿⣷⣿⣿⣆⠹⣯⣿⣻⣿⣿⣿⢀⣿⢿
⣿⣿⣿⣿⣿⣿⣿⣿⠘⣯⡿⡇⢸⣿⣿⣿⣿⣿⣿⣿⣧⡈⢿⣳⠘⡄⠻⣿⢾⣽⣟⡿⣿⢯⣿⡇⢸⣿⣿⣿⣿⣿⣿⡀⢾⣿⣿⣿⣿⣿⣿⣆⠹⣾⣷⣻⣿⡿⡇⢸⣿
⣿⣿⣿⣿⣿⣿⣿⣿⡇⢹⣿⠇⢸⣿⣿⣿⣿⣿⣿⣿⣿⣷⣄⠻⡇⢹⣆⠹⣟⣾⣽⣻⣟⣿⣽⠁⣾⣿⣿⣿⣿⣿⣿⣇⣿⣿⠿⠛⠛⠉⠙⠋⢀⠁⢘⣯⣿⣿⣧⠘⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⡈⣿⡃⢼⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣦⡙⠌⣿⣆⠘⣿⣞⡿⣞⡿⡞⢠⣿⣿⣿⣿⣿⡿⠛⠉⠁⢀⣀⣠⣤⣤⣶⣶⣶⡆⢻⣽⣞⡿⣷⠈⣿
⣿⣿⣿⣿⣿⣿⣿⣿⡿⠃⠘⠁⠉⠉⠉⠉⠉⠉⠉⠉⠉⠙⠛⠛⢿⣄⢻⣿⣧⠘⢯⣟⡿⣽⠁⣾⣿⣿⣿⣿⣿⡃⢀⢀⠘⠛⠿⢿⣻⣟⣯⣽⣻⣵⡀⢿⣯⣟⣿⢀⣿
⣿⣿⣿⣟⣿⣿⣿⣿⣶⣶⡆⢀⣿⣾⣿⣾⣷⣿⣶⠿⠚⠉⢀⢀⣤⣿⣷⣿⣿⣷⡈⢿⣻⢃⣼⣿⣿⣿⣿⣻⣿⣿⣿⡶⣦⣤⣄⣀⡀⠉⠛⠛⠷⣯⣳⠈⣾⡽⣾⢀⣿
⣿⢿⣿⣿⣻⣿⣿⣿⣿⣿⡿⠐⣿⣿⣿⣿⠿⠋⠁⢀⢀⣤⣾⣿⣿⣿⣿⣿⣿⣿⣿⣌⣥⣾⡿⣿⣿⣷⣿⣿⢿⣷⣿⣿⣟⣾⣽⣳⢯⣟⣶⣦⣤⡾⣟⣦⠘⣿⢾⡁⢺
⣿⣻⣿⣿⡷⣿⣿⣿⣿⣿⡗⣦⠸⡿⠋⠁⢀⢀⣠⣴⢿⣿⣽⣻⢽⣾⣟⣷⣿⣟⣿⣿⣿⣳⠿⣵⣧⣼⣿⣿⣿⣿⣿⣾⣿⣿⣿⣿⣿⣽⣳⣯⣿⣿⣿⣽⢀⢷⣻⠄⠘
⣿⢷⣻⣿⣿⣷⣻⣿⣿⣿⡷⠛⣁⢀⣀⣤⣶⣿⣛⡿⣿⣮⣽⡻⣿⣮⣽⣻⢯⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣯⢀⢸⣿⢀⡆
⠸⣟⣯⣿⣿⣷⢿⣽⣿⣿⣷⣿⣷⣆⠹⣿⣶⣯⠿⣿⣶⣟⣻⢿⣷⣽⣻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⢀⣯⣟⢀⡇
⣇⠹⣟⣾⣻⣿⣿⢾⡽⣿⣿⣿⣿⣿⣆⢹⣶⣿⣻⣷⣯⣟⣿⣿⣽⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⢀⡿⡇⢸⡇
⣿⣆⠹⣷⡻⣽⣿⣯⢿⣽⣻⣿⣿⣿⣿⣆⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠛⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠇⢸⣿⠇⣼⡇
⡙⠾⣆⠹⣿⣦⠛⣿⢯⣷⢿⡽⣿⣿⣿⣿⣆⠻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠃⠎⢸⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠏⢀⣿⣾⣣⡿⡇
⣿⣷⡌⢦⠙⣿⣿⣌⠻⣽⢯⣿⣽⣻⣿⣿⣿⣧⠩⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡏⢰⢣⠘⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠃⢀⢀⢿⣞⣷⢿⡇
⣿⣽⣆⠹⣧⠘⣿⣿⡷⣌⠙⢷⣯⡷⣟⣿⣿⣿⣷⡀⡹⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⣈⠃⣸⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠟⢀⣴⡧⢀⠸⣿⡽⣿⢀
⢻⣽⣿⡄⢻⣷⡈⢿⣿⣿⢧⢀⠙⢿⣻⡾⣽⣻⣿⣿⣄⠌⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠛⢁⣰⣾⣟⡿⢀⡄⢿⣟⣿⢀
⡄⢿⣿⣷⢀⠹⣟⣆⠻⣿⣿⣆⢀⣀⠉⠻⣿⡽⣯⣿⣿⣷⣈⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠋⢀⣠⠘⣯⣷⣿⡟⢀⢆⠸⣿⡟⢸
⣷⡈⢿⣿⣇⢱⡘⢿⣷⣬⣙⠿⣧⠘⣆⢀⠈⠻⣷⣟⣾⢿⣿⣆⠹⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠋⣠⡞⢡⣿⢀⣿⣿⣿⠇⡄⢸⡄⢻⡇⣼
⣿⣷⡈⢿⣿⡆⢣⡀⠙⢾⣟⣿⣿⣷⡈⠂⠘⣦⡈⠿⣯⣿⢾⣿⣆⠙⠻⠿⠿⠿⠿⡿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠿⠛⢋⣠⣾⡟⢠⣿⣿⢀⣿⣿⡟⢠⣿⢈⣧⠘⢠⣿
⣿⣿⣿⣄⠻⣿⡄⢳⡄⢆⡙⠾⣽⣿⣿⣆⡀⢹⡷⣄⠙⢿⣿⡾⣿⣆⢀⡀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⣀⣠⣴⡿⣯⠏⣠⣿⣿⡏⢸⣿⡿⢁⣿⣿⢀⣿⠆⢸⣿
⣿⣿⣿⣿⣦⡙⣿⣆⢻⡌⢿⣶⢤⣉⣙⣿⣷⡀⠙⠽⠷⠄⠹⣿⣟⣿⣆⢙⣋⣤⣤⣤⣄⣀⢀⢀⢀⢀⣾⣿⣟⡷⣯⡿⢃⣼⣿⣿⣿⠇⣼⡟⣡⣿⣿⣿⢀⡿⢠⠈⣿
⣿⣿⣿⣿⣿⣷⣮⣿⣿⣿⡌⠁⢤⣤⣤⣤⣬⣭⣴⣶⣶⣶⣆⠈⢻⣿⣿⣆⢻⣿⣿⣿⣿⣿⣿⣷⣶⣤⣌⣉⡘⠛⠻⠶⣿⣿⣿⣿⡟⣰⣫⣴⣿⣿⣿⣿⠄⣷⣿⣿⣿
*/

import javax.sound.midi.Soundbank;
import java.io.*;
import java.util.*;

public class D {

    /**
     * TODO 提交的时候一定要设置为 true
     */
    boolean submitFlag = true;

    private void solve(int k, Map<Integer, Integer> map) {
        int mod = 0;
        int index = 0;

//        System.out.println(Arrays.toString(num));
        for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
            Integer integer = entry.getKey();
            Integer integer2 = entry.getValue();
            if (integer2 > mod) {
                mod = integer2;
                index = integer;
            } else if (integer2 == mod && integer < index) {
                mod = integer2;
                index = integer;
            }
        }

        if (mod > 0) {
            // 补值
            int gg = k - index + 1;
            System.out.println((mod - 1) * k + gg);
        } else {
            System.out.println(0);
        }

    }

    private void run() throws IOException {
        //TODO 从这里开始读入题目输入
        int numberOfTestcases = nextInt();

        for (int t = 0; t < numberOfTestcases; t++) {
            int n = nextInt();
            int k = nextInt();
            // 余数累计
            Map<Integer, Integer> map = new HashMap<>();
            int[] num = new int[k];
            for (int i = 0; i < n; i++) {
                int data = nextInt();
                int key = data % k;
                if(key!=0){
                    Integer orDefault = map.getOrDefault(key, 0);
                    map.put(key, orDefault + 1);
                }
            }
            solve(k, map);
        }

    }

//    main以及输入输出========================================================================

    public static void main(String[] args) throws IOException {
        D solution = new D();
        solution.setReader();
        solution.run();
        solution.reader.close();
    }

    /**
     * 注意不同题目这里路径要设一下
     *
     * @throws IOException
     */
    private void setReader() throws IOException {
        if (submitFlag) {
            reader = new BufferedReader(new InputStreamReader(System.in));
        } else {
            String path = this.getClass().getResource("").getPath();
            File file = new File(path);
            while (!file.getName().equals("target")) {
                file = file.getParentFile();
            }
            String moduleName = file.getParentFile().getName();
            String projectPath = System.getProperty("user.dir");
            String modulePath = projectPath + "/" + moduleName + "/src/main/java/";
            String className = this.getClass().getName().replace(".", "\\");
            reader = new BufferedReader(new FileReader(modulePath + className + "input.txt"));
        }
    }

    BufferedReader reader;
    StringTokenizer tokenizer;

    int nextInt() throws IOException {
        return Integer.parseInt(nextToken());
    }

    long nextLong() throws IOException {
        return Long.parseLong(nextToken());
    }

    double nextDouble() throws IOException {
        return Double.parseDouble(nextToken());
    }

    String next() throws IOException {
        return nextToken();
    }

    String nextToken() throws IOException {
        while (tokenizer == null || !tokenizer.hasMoreTokens()) {
            tokenizer = new StringTokenizer(reader.readLine());
        }
        return tokenizer.nextToken();
    }
}


/*   盗图小能手
⣿⣿⣿⣿⣿⣿⡷⣯⢿⣿⣷⣻⢯⣿⡽⣻⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣇⠸⣿⣿⣆⠹⣿⣿⢾⣟⣯⣿⣿⣿⣿⣿⣿⣽⣻⣿⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣻⣽⡿⣿⣎⠙⣿⣞⣷⡌⢻⣟⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⣿⣿⣿⣿⣿⣿⡄⠹⣿⣿⡆⠻⣿⣟⣯⡿⣽⡿⣿⣿⣿⣿⣽⡷⣯⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣟⣷⣿⣿⣿⡀⠹⣟⣾⣟⣆⠹⣯⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡇⢠⡘⣿⣿⡄⠉⢿⣿⣽⡷⣿⣻⣿⣿⣿⣿⡝⣷⣯⢿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣯⢿⣾⢿⣿⡄⢄⠘⢿⣞⡿⣧⡈⢷⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡇⢸⣧⠘⣿⣷⠈⣦⠙⢿⣽⣷⣻⣽⣿⣿⣿⣿⣌⢿⣯⢿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣟⣯⣿⢿⣿⡆⢸⡷⡈⢻⡽⣷⡷⡄⠻⣽⣿⣿⡿⣿⣿⣿⣿⣿⣿⣷⣿⣿⣿⣿⣏⢰⣯⢷⠈⣿⡆⢹⢷⡌⠻⡾⢋⣱⣯⣿⣿⣿⣿⡆⢻⡿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⡎⣿⢾⡿⣿⡆⢸⣽⢻⣄⠹⣷⣟⣿⣄⠹⣟⣿⣿⣟⣿⣿⣿⣿⣿⣿⣽⣿⣿⣿⡇⢸⣯⣟⣧⠘⣷⠈⡯⠛⢀⡐⢾⣟⣷⣻⣿⣿⣿⡿⡌⢿⣻⣿⣿
⣿⣿⣿⣿⣿⣿⣧⢸⡿⣟⣿⡇⢸⣯⣟⣮⢧⡈⢿⣞⡿⣦⠘⠏⣹⣿⣽⢿⣿⣿⣿⣿⣯⣿⣿⣿⡇⢸⣿⣿⣾⡆⠹⢀⣠⣾⣟⣷⡈⢿⣞⣯⢿⣿⣿⣿⢷⠘⣯⣿⣿
⣿⣿⣿⣿⣿⣿⣿⡈⣿⢿⣽⡇⠘⠛⠛⠛⠓⠓⠈⠛⠛⠟⠇⢀⢿⣻⣿⣯⢿⣿⣿⣿⣷⢿⣿⣿⠁⣾⣿⣿⣿⣧⡄⠇⣹⣿⣾⣯⣿⡄⠻⣽⣯⢿⣻⣿⣿⡇⢹⣾⣿
⣿⣿⣿⣿⣿⣿⣿⡇⢹⣿⡽⡇⢸⣿⣿⣿⣿⣿⣞⣆⠰⣶⣶⡄⢀⢻⡿⣯⣿⡽⣿⣿⣿⢯⣟⡿⢀⣿⣿⣿⣿⣿⣧⠐⣸⣿⣿⣷⣿⣿⣆⠹⣯⣿⣻⣿⣿⣿⢀⣿⢿
⣿⣿⣿⣿⣿⣿⣿⣿⠘⣯⡿⡇⢸⣿⣿⣿⣿⣿⣿⣿⣧⡈⢿⣳⠘⡄⠻⣿⢾⣽⣟⡿⣿⢯⣿⡇⢸⣿⣿⣿⣿⣿⣿⡀⢾⣿⣿⣿⣿⣿⣿⣆⠹⣾⣷⣻⣿⡿⡇⢸⣿
⣿⣿⣿⣿⣿⣿⣿⣿⡇⢹⣿⠇⢸⣿⣿⣿⣿⣿⣿⣿⣿⣷⣄⠻⡇⢹⣆⠹⣟⣾⣽⣻⣟⣿⣽⠁⣾⣿⣿⣿⣿⣿⣿⣇⣿⣿⠿⠛⠛⠉⠙⠋⢀⠁⢘⣯⣿⣿⣧⠘⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⡈⣿⡃⢼⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣦⡙⠌⣿⣆⠘⣿⣞⡿⣞⡿⡞⢠⣿⣿⣿⣿⣿⡿⠛⠉⠁⢀⣀⣠⣤⣤⣶⣶⣶⡆⢻⣽⣞⡿⣷⠈⣿
⣿⣿⣿⣿⣿⣿⣿⣿⡿⠃⠘⠁⠉⠉⠉⠉⠉⠉⠉⠉⠉⠙⠛⠛⢿⣄⢻⣿⣧⠘⢯⣟⡿⣽⠁⣾⣿⣿⣿⣿⣿⡃⢀⢀⠘⠛⠿⢿⣻⣟⣯⣽⣻⣵⡀⢿⣯⣟⣿⢀⣿
⣿⣿⣿⣟⣿⣿⣿⣿⣶⣶⡆⢀⣿⣾⣿⣾⣷⣿⣶⠿⠚⠉⢀⢀⣤⣿⣷⣿⣿⣷⡈⢿⣻⢃⣼⣿⣿⣿⣿⣻⣿⣿⣿⡶⣦⣤⣄⣀⡀⠉⠛⠛⠷⣯⣳⠈⣾⡽⣾⢀⣿
⣿⢿⣿⣿⣻⣿⣿⣿⣿⣿⡿⠐⣿⣿⣿⣿⠿⠋⠁⢀⢀⣤⣾⣿⣿⣿⣿⣿⣿⣿⣿⣌⣥⣾⡿⣿⣿⣷⣿⣿⢿⣷⣿⣿⣟⣾⣽⣳⢯⣟⣶⣦⣤⡾⣟⣦⠘⣿⢾⡁⢺
⣿⣻⣿⣿⡷⣿⣿⣿⣿⣿⡗⣦⠸⡿⠋⠁⢀⢀⣠⣴⢿⣿⣽⣻⢽⣾⣟⣷⣿⣟⣿⣿⣿⣳⠿⣵⣧⣼⣿⣿⣿⣿⣿⣾⣿⣿⣿⣿⣿⣽⣳⣯⣿⣿⣿⣽⢀⢷⣻⠄⠘
⣿⢷⣻⣿⣿⣷⣻⣿⣿⣿⡷⠛⣁⢀⣀⣤⣶⣿⣛⡿⣿⣮⣽⡻⣿⣮⣽⣻⢯⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣯⢀⢸⣿⢀⡆
⠸⣟⣯⣿⣿⣷⢿⣽⣿⣿⣷⣿⣷⣆⠹⣿⣶⣯⠿⣿⣶⣟⣻⢿⣷⣽⣻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⢀⣯⣟⢀⡇
⣇⠹⣟⣾⣻⣿⣿⢾⡽⣿⣿⣿⣿⣿⣆⢹⣶⣿⣻⣷⣯⣟⣿⣿⣽⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⢀⡿⡇⢸⡇
⣿⣆⠹⣷⡻⣽⣿⣯⢿⣽⣻⣿⣿⣿⣿⣆⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠛⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠇⢸⣿⠇⣼⡇
⡙⠾⣆⠹⣿⣦⠛⣿⢯⣷⢿⡽⣿⣿⣿⣿⣆⠻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠃⠎⢸⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠏⢀⣿⣾⣣⡿⡇
⣿⣷⡌⢦⠙⣿⣿⣌⠻⣽⢯⣿⣽⣻⣿⣿⣿⣧⠩⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡏⢰⢣⠘⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠃⢀⢀⢿⣞⣷⢿⡇
⣿⣽⣆⠹⣧⠘⣿⣿⡷⣌⠙⢷⣯⡷⣟⣿⣿⣿⣷⡀⡹⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⣈⠃⣸⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠟⢀⣴⡧⢀⠸⣿⡽⣿⢀
⢻⣽⣿⡄⢻⣷⡈⢿⣿⣿⢧⢀⠙⢿⣻⡾⣽⣻⣿⣿⣄⠌⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠛⢁⣰⣾⣟⡿⢀⡄⢿⣟⣿⢀
⡄⢿⣿⣷⢀⠹⣟⣆⠻⣿⣿⣆⢀⣀⠉⠻⣿⡽⣯⣿⣿⣷⣈⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠋⢀⣠⠘⣯⣷⣿⡟⢀⢆⠸⣿⡟⢸
⣷⡈⢿⣿⣇⢱⡘⢿⣷⣬⣙⠿⣧⠘⣆⢀⠈⠻⣷⣟⣾⢿⣿⣆⠹⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠋⣠⡞⢡⣿⢀⣿⣿⣿⠇⡄⢸⡄⢻⡇⣼
⣿⣷⡈⢿⣿⡆⢣⡀⠙⢾⣟⣿⣿⣷⡈⠂⠘⣦⡈⠿⣯⣿⢾⣿⣆⠙⠻⠿⠿⠿⠿⡿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠿⠛⢋⣠⣾⡟⢠⣿⣿⢀⣿⣿⡟⢠⣿⢈⣧⠘⢠⣿
⣿⣿⣿⣄⠻⣿⡄⢳⡄⢆⡙⠾⣽⣿⣿⣆⡀⢹⡷⣄⠙⢿⣿⡾⣿⣆⢀⡀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⣀⣠⣴⡿⣯⠏⣠⣿⣿⡏⢸⣿⡿⢁⣿⣿⢀⣿⠆⢸⣿
⣿⣿⣿⣿⣦⡙⣿⣆⢻⡌⢿⣶⢤⣉⣙⣿⣷⡀⠙⠽⠷⠄⠹⣿⣟⣿⣆⢙⣋⣤⣤⣤⣄⣀⢀⢀⢀⢀⣾⣿⣟⡷⣯⡿⢃⣼⣿⣿⣿⠇⣼⡟⣡⣿⣿⣿⢀⡿⢠⠈⣿
⣿⣿⣿⣿⣿⣷⣮⣿⣿⣿⡌⠁⢤⣤⣤⣤⣬⣭⣴⣶⣶⣶⣆⠈⢻⣿⣿⣆⢻⣿⣿⣿⣿⣿⣿⣷⣶⣤⣌⣉⡘⠛⠻⠶⣿⣿⣿⣿⡟⣰⣫⣴⣿⣿⣿⣿⠄⣷⣿⣿⣿
*/

import javax.sound.midi.Soundbank;
import java.io.*;
import java.util.*;

public class D {

    /**
     * TODO 提交的时候一定要设置为 true
     */
    boolean submitFlag = true;

    private void run() throws IOException {
        //TODO 从这里开始读入题目输入
        int numberOfTestcases = nextInt();

        for (int t = 0; t < numberOfTestcases; t++) {
            int n = nextInt();
            int k = nextInt();
            long ans = -1;
            // 余数累计
            Map<Integer, Long> map = new HashMap<>();
            for (int i = 0; i < n; i++) {
                int data = nextInt();
                int key = data % k;
                if (key != 0) {
                    Long orDefault = map.getOrDefault(key, 0);
                    orDefault++;
                    map.put(key, orDefault);
                    ans = Math.max(ans, orDefault * k - key);
                }
            }
            System.out.println(ans + 1);
        }
    }

//    main以及输入输出========================================================================

    public static void main(String[] args) throws IOException {
        D solution = new D();
        solution.setReader();
        solution.run();
        solution.reader.close();
    }

    /**
     * 注意不同题目这里路径要设一下
     *
     * @throws IOException
     */
    private void setReader() throws IOException {
        if (submitFlag) {
            reader = new BufferedReader(new InputStreamReader(System.in));
        } else {
            String path = this.getClass().getResource("").getPath();
            File file = new File(path);
            while (!file.getName().equals("target")) {
                file = file.getParentFile();
            }
            String moduleName = file.getParentFile().getName();
            String projectPath = System.getProperty("user.dir");
            String modulePath = projectPath + "/" + moduleName + "/src/main/java/";
            String className = this.getClass().getName().replace(".", "\\");
            reader = new BufferedReader(new FileReader(modulePath + className + "input.txt"));
        }
    }

    BufferedReader reader;
    StringTokenizer tokenizer;

    int nextInt() throws IOException {
        return Integer.parseInt(nextToken());
    }

    long nextLong() throws IOException {
        return Long.parseLong(nextToken());
    }

    double nextDouble() throws IOException {
        return Double.parseDouble(nextToken());
    }

    String next() throws IOException {
        return nextToken();
    }

    String nextToken() throws IOException {
        while (tokenizer == null || !tokenizer.hasMoreTokens()) {
            tokenizer = new StringTokenizer(reader.readLine());
        }
        return tokenizer.nextToken();
    }
}


/*   盗图小能手
⣿⣿⣿⣿⣿⣿⡷⣯⢿⣿⣷⣻⢯⣿⡽⣻⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣇⠸⣿⣿⣆⠹⣿⣿⢾⣟⣯⣿⣿⣿⣿⣿⣿⣽⣻⣿⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣻⣽⡿⣿⣎⠙⣿⣞⣷⡌⢻⣟⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⣿⣿⣿⣿⣿⣿⡄⠹⣿⣿⡆⠻⣿⣟⣯⡿⣽⡿⣿⣿⣿⣿⣽⡷⣯⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣟⣷⣿⣿⣿⡀⠹⣟⣾⣟⣆⠹⣯⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡇⢠⡘⣿⣿⡄⠉⢿⣿⣽⡷⣿⣻⣿⣿⣿⣿⡝⣷⣯⢿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣯⢿⣾⢿⣿⡄⢄⠘⢿⣞⡿⣧⡈⢷⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡇⢸⣧⠘⣿⣷⠈⣦⠙⢿⣽⣷⣻⣽⣿⣿⣿⣿⣌⢿⣯⢿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣟⣯⣿⢿⣿⡆⢸⡷⡈⢻⡽⣷⡷⡄⠻⣽⣿⣿⡿⣿⣿⣿⣿⣿⣿⣷⣿⣿⣿⣿⣏⢰⣯⢷⠈⣿⡆⢹⢷⡌⠻⡾⢋⣱⣯⣿⣿⣿⣿⡆⢻⡿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⡎⣿⢾⡿⣿⡆⢸⣽⢻⣄⠹⣷⣟⣿⣄⠹⣟⣿⣿⣟⣿⣿⣿⣿⣿⣿⣽⣿⣿⣿⡇⢸⣯⣟⣧⠘⣷⠈⡯⠛⢀⡐⢾⣟⣷⣻⣿⣿⣿⡿⡌⢿⣻⣿⣿
⣿⣿⣿⣿⣿⣿⣧⢸⡿⣟⣿⡇⢸⣯⣟⣮⢧⡈⢿⣞⡿⣦⠘⠏⣹⣿⣽⢿⣿⣿⣿⣿⣯⣿⣿⣿⡇⢸⣿⣿⣾⡆⠹⢀⣠⣾⣟⣷⡈⢿⣞⣯⢿⣿⣿⣿⢷⠘⣯⣿⣿
⣿⣿⣿⣿⣿⣿⣿⡈⣿⢿⣽⡇⠘⠛⠛⠛⠓⠓⠈⠛⠛⠟⠇⢀⢿⣻⣿⣯⢿⣿⣿⣿⣷⢿⣿⣿⠁⣾⣿⣿⣿⣧⡄⠇⣹⣿⣾⣯⣿⡄⠻⣽⣯⢿⣻⣿⣿⡇⢹⣾⣿
⣿⣿⣿⣿⣿⣿⣿⡇⢹⣿⡽⡇⢸⣿⣿⣿⣿⣿⣞⣆⠰⣶⣶⡄⢀⢻⡿⣯⣿⡽⣿⣿⣿⢯⣟⡿⢀⣿⣿⣿⣿⣿⣧⠐⣸⣿⣿⣷⣿⣿⣆⠹⣯⣿⣻⣿⣿⣿⢀⣿⢿
⣿⣿⣿⣿⣿⣿⣿⣿⠘⣯⡿⡇⢸⣿⣿⣿⣿⣿⣿⣿⣧⡈⢿⣳⠘⡄⠻⣿⢾⣽⣟⡿⣿⢯⣿⡇⢸⣿⣿⣿⣿⣿⣿⡀⢾⣿⣿⣿⣿⣿⣿⣆⠹⣾⣷⣻⣿⡿⡇⢸⣿
⣿⣿⣿⣿⣿⣿⣿⣿⡇⢹⣿⠇⢸⣿⣿⣿⣿⣿⣿⣿⣿⣷⣄⠻⡇⢹⣆⠹⣟⣾⣽⣻⣟⣿⣽⠁⣾⣿⣿⣿⣿⣿⣿⣇⣿⣿⠿⠛⠛⠉⠙⠋⢀⠁⢘⣯⣿⣿⣧⠘⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⡈⣿⡃⢼⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣦⡙⠌⣿⣆⠘⣿⣞⡿⣞⡿⡞⢠⣿⣿⣿⣿⣿⡿⠛⠉⠁⢀⣀⣠⣤⣤⣶⣶⣶⡆⢻⣽⣞⡿⣷⠈⣿
⣿⣿⣿⣿⣿⣿⣿⣿⡿⠃⠘⠁⠉⠉⠉⠉⠉⠉⠉⠉⠉⠙⠛⠛⢿⣄⢻⣿⣧⠘⢯⣟⡿⣽⠁⣾⣿⣿⣿⣿⣿⡃⢀⢀⠘⠛⠿⢿⣻⣟⣯⣽⣻⣵⡀⢿⣯⣟⣿⢀⣿
⣿⣿⣿⣟⣿⣿⣿⣿⣶⣶⡆⢀⣿⣾⣿⣾⣷⣿⣶⠿⠚⠉⢀⢀⣤⣿⣷⣿⣿⣷⡈⢿⣻⢃⣼⣿⣿⣿⣿⣻⣿⣿⣿⡶⣦⣤⣄⣀⡀⠉⠛⠛⠷⣯⣳⠈⣾⡽⣾⢀⣿
⣿⢿⣿⣿⣻⣿⣿⣿⣿⣿⡿⠐⣿⣿⣿⣿⠿⠋⠁⢀⢀⣤⣾⣿⣿⣿⣿⣿⣿⣿⣿⣌⣥⣾⡿⣿⣿⣷⣿⣿⢿⣷⣿⣿⣟⣾⣽⣳⢯⣟⣶⣦⣤⡾⣟⣦⠘⣿⢾⡁⢺
⣿⣻⣿⣿⡷⣿⣿⣿⣿⣿⡗⣦⠸⡿⠋⠁⢀⢀⣠⣴⢿⣿⣽⣻⢽⣾⣟⣷⣿⣟⣿⣿⣿⣳⠿⣵⣧⣼⣿⣿⣿⣿⣿⣾⣿⣿⣿⣿⣿⣽⣳⣯⣿⣿⣿⣽⢀⢷⣻⠄⠘
⣿⢷⣻⣿⣿⣷⣻⣿⣿⣿⡷⠛⣁⢀⣀⣤⣶⣿⣛⡿⣿⣮⣽⡻⣿⣮⣽⣻⢯⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣯⢀⢸⣿⢀⡆
⠸⣟⣯⣿⣿⣷⢿⣽⣿⣿⣷⣿⣷⣆⠹⣿⣶⣯⠿⣿⣶⣟⣻⢿⣷⣽⣻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⢀⣯⣟⢀⡇
⣇⠹⣟⣾⣻⣿⣿⢾⡽⣿⣿⣿⣿⣿⣆⢹⣶⣿⣻⣷⣯⣟⣿⣿⣽⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⢀⡿⡇⢸⡇
⣿⣆⠹⣷⡻⣽⣿⣯⢿⣽⣻⣿⣿⣿⣿⣆⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠛⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠇⢸⣿⠇⣼⡇
⡙⠾⣆⠹⣿⣦⠛⣿⢯⣷⢿⡽⣿⣿⣿⣿⣆⠻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠃⠎⢸⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠏⢀⣿⣾⣣⡿⡇
⣿⣷⡌⢦⠙⣿⣿⣌⠻⣽⢯⣿⣽⣻⣿⣿⣿⣧⠩⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡏⢰⢣⠘⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠃⢀⢀⢿⣞⣷⢿⡇
⣿⣽⣆⠹⣧⠘⣿⣿⡷⣌⠙⢷⣯⡷⣟⣿⣿⣿⣷⡀⡹⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⣈⠃⣸⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠟⢀⣴⡧⢀⠸⣿⡽⣿⢀
⢻⣽⣿⡄⢻⣷⡈⢿⣿⣿⢧⢀⠙⢿⣻⡾⣽⣻⣿⣿⣄⠌⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠛⢁⣰⣾⣟⡿⢀⡄⢿⣟⣿⢀
⡄⢿⣿⣷⢀⠹⣟⣆⠻⣿⣿⣆⢀⣀⠉⠻⣿⡽⣯⣿⣿⣷⣈⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠋⢀⣠⠘⣯⣷⣿⡟⢀⢆⠸⣿⡟⢸
⣷⡈⢿⣿⣇⢱⡘⢿⣷⣬⣙⠿⣧⠘⣆⢀⠈⠻⣷⣟⣾⢿⣿⣆⠹⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠋⣠⡞⢡⣿⢀⣿⣿⣿⠇⡄⢸⡄⢻⡇⣼
⣿⣷⡈⢿⣿⡆⢣⡀⠙⢾⣟⣿⣿⣷⡈⠂⠘⣦⡈⠿⣯⣿⢾⣿⣆⠙⠻⠿⠿⠿⠿⡿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠿⠛⢋⣠⣾⡟⢠⣿⣿⢀⣿⣿⡟⢠⣿⢈⣧⠘⢠⣿
⣿⣿⣿⣄⠻⣿⡄⢳⡄⢆⡙⠾⣽⣿⣿⣆⡀⢹⡷⣄⠙⢿⣿⡾⣿⣆⢀⡀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⣀⣠⣴⡿⣯⠏⣠⣿⣿⡏⢸⣿⡿⢁⣿⣿⢀⣿⠆⢸⣿
⣿⣿⣿⣿⣦⡙⣿⣆⢻⡌⢿⣶⢤⣉⣙⣿⣷⡀⠙⠽⠷⠄⠹⣿⣟⣿⣆⢙⣋⣤⣤⣤⣄⣀⢀⢀⢀⢀⣾⣿⣟⡷⣯⡿⢃⣼⣿⣿⣿⠇⣼⡟⣡⣿⣿⣿⢀⡿⢠⠈⣿
⣿⣿⣿⣿⣿⣷⣮⣿⣿⣿⡌⠁⢤⣤⣤⣤⣬⣭⣴⣶⣶⣶⣆⠈⢻⣿⣿⣆⢻⣿⣿⣿⣿⣿⣿⣷⣶⣤⣌⣉⡘⠛⠻⠶⣿⣿⣿⣿⡟⣰⣫⣴⣿⣿⣿⣿⠄⣷⣿⣿⣿
*/

import javax.sound.midi.Soundbank;
import java.io.*;
import java.util.*;

public class D {

    /**
     * TODO 提交的时候一定要设置为 true
     */
    boolean submitFlag = true;

    private void solve(int[] num) {
        int mod = 0;
        int index = 0;

//        System.out.println(Arrays.toString(num));

        for (int i = 1; i < num.length; i++) {
            if (num[i] > mod) {
                mod = num[i];
                index = i;
            }
        }

        if (mod > 0) {
            // 补值
            int gg = num.length - index+1;
            System.out.println((mod - 1) * num.length + gg);
        } else {
            System.out.println(0);
        }

    }

    private void run() throws IOException {
        //TODO 从这里开始读入题目输入
        int numberOfTestcases = nextInt();

        for (int t = 0; t < numberOfTestcases; t++) {
            int n = nextInt();
            int k = nextInt();
//            int[] a = new int[n];
            // 余数累计
            int[] num = new int[k];
            for (int i = 0; i < n; i++) {
                int data = nextInt();
                num[data % k]++;
            }
            solve( num);
        }

    }

//    main以及输入输出========================================================================

    public static void main(String[] args) throws IOException {
        D solution = new D();
        solution.setReader();
        solution.run();
        solution.reader.close();
    }

    /**
     * 注意不同题目这里路径要设一下
     *
     * @throws IOException
     */
    private void setReader() throws IOException {
        if (submitFlag) {
            reader = new BufferedReader(new InputStreamReader(System.in));
        } else {
            String path = this.getClass().getResource("").getPath();
            File file = new File(path);
            while (!file.getName().equals("target")) {
                file = file.getParentFile();
            }
            String moduleName = file.getParentFile().getName();
            String projectPath = System.getProperty("user.dir");
            String modulePath = projectPath + "/" + moduleName + "/src/main/java/";
            String className = this.getClass().getName().replace(".", "\\");
            reader = new BufferedReader(new FileReader(modulePath + className + "input.txt"));
        }
    }

    BufferedReader reader;
    StringTokenizer tokenizer;

    int nextInt() throws IOException {
        return Integer.parseInt(nextToken());
    }

    long nextLong() throws IOException {
        return Long.parseLong(nextToken());
    }

    double nextDouble() throws IOException {
        return Double.parseDouble(nextToken());
    }

    String next() throws IOException {
        return nextToken();
    }

    String nextToken() throws IOException {
        while (tokenizer == null || !tokenizer.hasMoreTokens()) {
            tokenizer = new StringTokenizer(reader.readLine());
        }
        return tokenizer.nextToken();
    }
}


/*   盗图小能手
⣿⣿⣿⣿⣿⣿⡷⣯⢿⣿⣷⣻⢯⣿⡽⣻⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣇⠸⣿⣿⣆⠹⣿⣿⢾⣟⣯⣿⣿⣿⣿⣿⣿⣽⣻⣿⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣻⣽⡿⣿⣎⠙⣿⣞⣷⡌⢻⣟⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⣿⣿⣿⣿⣿⣿⡄⠹⣿⣿⡆⠻⣿⣟⣯⡿⣽⡿⣿⣿⣿⣿⣽⡷⣯⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣟⣷⣿⣿⣿⡀⠹⣟⣾⣟⣆⠹⣯⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡇⢠⡘⣿⣿⡄⠉⢿⣿⣽⡷⣿⣻⣿⣿⣿⣿⡝⣷⣯⢿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣯⢿⣾⢿⣿⡄⢄⠘⢿⣞⡿⣧⡈⢷⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡇⢸⣧⠘⣿⣷⠈⣦⠙⢿⣽⣷⣻⣽⣿⣿⣿⣿⣌⢿⣯⢿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣟⣯⣿⢿⣿⡆⢸⡷⡈⢻⡽⣷⡷⡄⠻⣽⣿⣿⡿⣿⣿⣿⣿⣿⣿⣷⣿⣿⣿⣿⣏⢰⣯⢷⠈⣿⡆⢹⢷⡌⠻⡾⢋⣱⣯⣿⣿⣿⣿⡆⢻⡿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⡎⣿⢾⡿⣿⡆⢸⣽⢻⣄⠹⣷⣟⣿⣄⠹⣟⣿⣿⣟⣿⣿⣿⣿⣿⣿⣽⣿⣿⣿⡇⢸⣯⣟⣧⠘⣷⠈⡯⠛⢀⡐⢾⣟⣷⣻⣿⣿⣿⡿⡌⢿⣻⣿⣿
⣿⣿⣿⣿⣿⣿⣧⢸⡿⣟⣿⡇⢸⣯⣟⣮⢧⡈⢿⣞⡿⣦⠘⠏⣹⣿⣽⢿⣿⣿⣿⣿⣯⣿⣿⣿⡇⢸⣿⣿⣾⡆⠹⢀⣠⣾⣟⣷⡈⢿⣞⣯⢿⣿⣿⣿⢷⠘⣯⣿⣿
⣿⣿⣿⣿⣿⣿⣿⡈⣿⢿⣽⡇⠘⠛⠛⠛⠓⠓⠈⠛⠛⠟⠇⢀⢿⣻⣿⣯⢿⣿⣿⣿⣷⢿⣿⣿⠁⣾⣿⣿⣿⣧⡄⠇⣹⣿⣾⣯⣿⡄⠻⣽⣯⢿⣻⣿⣿⡇⢹⣾⣿
⣿⣿⣿⣿⣿⣿⣿⡇⢹⣿⡽⡇⢸⣿⣿⣿⣿⣿⣞⣆⠰⣶⣶⡄⢀⢻⡿⣯⣿⡽⣿⣿⣿⢯⣟⡿⢀⣿⣿⣿⣿⣿⣧⠐⣸⣿⣿⣷⣿⣿⣆⠹⣯⣿⣻⣿⣿⣿⢀⣿⢿
⣿⣿⣿⣿⣿⣿⣿⣿⠘⣯⡿⡇⢸⣿⣿⣿⣿⣿⣿⣿⣧⡈⢿⣳⠘⡄⠻⣿⢾⣽⣟⡿⣿⢯⣿⡇⢸⣿⣿⣿⣿⣿⣿⡀⢾⣿⣿⣿⣿⣿⣿⣆⠹⣾⣷⣻⣿⡿⡇⢸⣿
⣿⣿⣿⣿⣿⣿⣿⣿⡇⢹⣿⠇⢸⣿⣿⣿⣿⣿⣿⣿⣿⣷⣄⠻⡇⢹⣆⠹⣟⣾⣽⣻⣟⣿⣽⠁⣾⣿⣿⣿⣿⣿⣿⣇⣿⣿⠿⠛⠛⠉⠙⠋⢀⠁⢘⣯⣿⣿⣧⠘⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⡈⣿⡃⢼⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣦⡙⠌⣿⣆⠘⣿⣞⡿⣞⡿⡞⢠⣿⣿⣿⣿⣿⡿⠛⠉⠁⢀⣀⣠⣤⣤⣶⣶⣶⡆⢻⣽⣞⡿⣷⠈⣿
⣿⣿⣿⣿⣿⣿⣿⣿⡿⠃⠘⠁⠉⠉⠉⠉⠉⠉⠉⠉⠉⠙⠛⠛⢿⣄⢻⣿⣧⠘⢯⣟⡿⣽⠁⣾⣿⣿⣿⣿⣿⡃⢀⢀⠘⠛⠿⢿⣻⣟⣯⣽⣻⣵⡀⢿⣯⣟⣿⢀⣿
⣿⣿⣿⣟⣿⣿⣿⣿⣶⣶⡆⢀⣿⣾⣿⣾⣷⣿⣶⠿⠚⠉⢀⢀⣤⣿⣷⣿⣿⣷⡈⢿⣻⢃⣼⣿⣿⣿⣿⣻⣿⣿⣿⡶⣦⣤⣄⣀⡀⠉⠛⠛⠷⣯⣳⠈⣾⡽⣾⢀⣿
⣿⢿⣿⣿⣻⣿⣿⣿⣿⣿⡿⠐⣿⣿⣿⣿⠿⠋⠁⢀⢀⣤⣾⣿⣿⣿⣿⣿⣿⣿⣿⣌⣥⣾⡿⣿⣿⣷⣿⣿⢿⣷⣿⣿⣟⣾⣽⣳⢯⣟⣶⣦⣤⡾⣟⣦⠘⣿⢾⡁⢺
⣿⣻⣿⣿⡷⣿⣿⣿⣿⣿⡗⣦⠸⡿⠋⠁⢀⢀⣠⣴⢿⣿⣽⣻⢽⣾⣟⣷⣿⣟⣿⣿⣿⣳⠿⣵⣧⣼⣿⣿⣿⣿⣿⣾⣿⣿⣿⣿⣿⣽⣳⣯⣿⣿⣿⣽⢀⢷⣻⠄⠘
⣿⢷⣻⣿⣿⣷⣻⣿⣿⣿⡷⠛⣁⢀⣀⣤⣶⣿⣛⡿⣿⣮⣽⡻⣿⣮⣽⣻⢯⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣯⢀⢸⣿⢀⡆
⠸⣟⣯⣿⣿⣷⢿⣽⣿⣿⣷⣿⣷⣆⠹⣿⣶⣯⠿⣿⣶⣟⣻⢿⣷⣽⣻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⢀⣯⣟⢀⡇
⣇⠹⣟⣾⣻⣿⣿⢾⡽⣿⣿⣿⣿⣿⣆⢹⣶⣿⣻⣷⣯⣟⣿⣿⣽⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⢀⡿⡇⢸⡇
⣿⣆⠹⣷⡻⣽⣿⣯⢿⣽⣻⣿⣿⣿⣿⣆⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠛⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠇⢸⣿⠇⣼⡇
⡙⠾⣆⠹⣿⣦⠛⣿⢯⣷⢿⡽⣿⣿⣿⣿⣆⠻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠃⠎⢸⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠏⢀⣿⣾⣣⡿⡇
⣿⣷⡌⢦⠙⣿⣿⣌⠻⣽⢯⣿⣽⣻⣿⣿⣿⣧⠩⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡏⢰⢣⠘⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠃⢀⢀⢿⣞⣷⢿⡇
⣿⣽⣆⠹⣧⠘⣿⣿⡷⣌⠙⢷⣯⡷⣟⣿⣿⣿⣷⡀⡹⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⣈⠃⣸⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠟⢀⣴⡧⢀⠸⣿⡽⣿⢀
⢻⣽⣿⡄⢻⣷⡈⢿⣿⣿⢧⢀⠙⢿⣻⡾⣽⣻⣿⣿⣄⠌⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠛⢁⣰⣾⣟⡿⢀⡄⢿⣟⣿⢀
⡄⢿⣿⣷⢀⠹⣟⣆⠻⣿⣿⣆⢀⣀⠉⠻⣿⡽⣯⣿⣿⣷⣈⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠋⢀⣠⠘⣯⣷⣿⡟⢀⢆⠸⣿⡟⢸
⣷⡈⢿⣿⣇⢱⡘⢿⣷⣬⣙⠿⣧⠘⣆⢀⠈⠻⣷⣟⣾⢿⣿⣆⠹⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠋⣠⡞⢡⣿⢀⣿⣿⣿⠇⡄⢸⡄⢻⡇⣼
⣿⣷⡈⢿⣿⡆⢣⡀⠙⢾⣟⣿⣿⣷⡈⠂⠘⣦⡈⠿⣯⣿⢾⣿⣆⠙⠻⠿⠿⠿⠿⡿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠿⠛⢋⣠⣾⡟⢠⣿⣿⢀⣿⣿⡟⢠⣿⢈⣧⠘⢠⣿
⣿⣿⣿⣄⠻⣿⡄⢳⡄⢆⡙⠾⣽⣿⣿⣆⡀⢹⡷⣄⠙⢿⣿⡾⣿⣆⢀⡀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⢀⣀⣠⣴⡿⣯⠏⣠⣿⣿⡏⢸⣿⡿⢁⣿⣿⢀⣿⠆⢸⣿
⣿⣿⣿⣿⣦⡙⣿⣆⢻⡌⢿⣶⢤⣉⣙⣿⣷⡀⠙⠽⠷⠄⠹⣿⣟⣿⣆⢙⣋⣤⣤⣤⣄⣀⢀⢀⢀⢀⣾⣿⣟⡷⣯⡿⢃⣼⣿⣿⣿⠇⣼⡟⣡⣿⣿⣿⢀⡿⢠⠈⣿
⣿⣿⣿⣿⣿⣷⣮⣿⣿⣿⡌⠁⢤⣤⣤⣤⣬⣭⣴⣶⣶⣶⣆⠈⢻⣿⣿⣆⢻⣿⣿⣿⣿⣿⣿⣷⣶⣤⣌⣉⡘⠛⠻⠶⣿⣿⣿⣿⡟⣰⣫⣴⣿⣿⣿⣿⠄⣷⣿⣿⣿
*/

import javax.sound.midi.Soundbank;
import java.io.*;
import java.util.*;

public class D {

    /**
     * TODO 提交的时候一定要设置为 true
     */
    boolean submitFlag = true;

    private void solve(int n, int k, int[] a) {
        for (int i = 0; i < a.length; i++) {
            a[i] = a[i] % k;
        }
        Arrays.sort(a);
        int ansNum = 0;
        int ans = 0;
        int i = 0;
        for (i = 0; i < a.length; i++) {
            if (a[i] != 0) {
                break;
            }
        }

        int mod = 0;
        int modNum = 0;
        for (; i < a.length; ) {
            mod = a[i];
            modNum = 0;
            while (i < a.length && a[i] == mod) {
                modNum++;
                i++;
            }
            if (modNum > ansNum) {
                ansNum = modNum;
                ans = mod;
            }
        }

        if (ansNum > 0) {
            // 补值
            int gg = k - ans + 1;
            System.out.println((ansNum - 1) * k + gg);
        } else {
            System.out.println(0);
        }

    }

    private void run() throws IOException {
        //TODO 从这里开始读入题目输入
        int numberOfTestcases = nextInt();

        for (int t = 0; t < numberOfTestcases; t++) {
            int n = nextInt();
            int k = nextInt();
            int[] a = new int[n];
            for (int i = 0; i < n; i++) {
                a[i] = nextInt();

            }
            solve(n, k, a);
        }

    }

//    main以及输入输出========================================================================

    public static void main(String[] args) throws IOException {
        D solution = new D();
        solution.setReader();
        solution.run();
        solution.reader.close();
    }

    /**
     * 注意不同题目这里路径要设一下
     *
     * @throws IOException
     */
    private void setReader() throws IOException {
        if (submitFlag) {
            reader = new BufferedReader(new InputStreamReader(System.in));
        } else {
            String path = this.getClass().getResource("").getPath();
            File file = new File(path);
            while (!file.getName().equals("target")) {
                file = file.getParentFile();
            }
            String moduleName = file.getParentFile().getName();
            String projectPath = System.getProperty("user.dir");
            String modulePath = projectPath + "/" + moduleName + "/src/main/java/";
            String className = this.getClass().getName().replace(".", "\\");
            reader = new BufferedReader(new FileReader(modulePath + className + "input.txt"));
        }
    }

    BufferedReader reader;
    StringTokenizer tokenizer;

    int nextInt() throws IOException {
        return Integer.parseInt(nextToken());
    }

    long nextLong() throws IOException {
        return Long.parseLong(nextToken());
    }

    double nextDouble() throws IOException {
        return Double.parseDouble(nextToken());
    }

    String next() throws IOException {
        return nextToken();
    }

    String nextToken() throws IOException {
        while (tokenizer == null || !tokenizer.hasMoreTokens()) {
            tokenizer = new StringTokenizer(reader.readLine());
        }
        return tokenizer.nextToken();
    }
}