In the Mathophobia lottery, people select an ordered sequence of 4 distinct numbers from 1 to 10. The winning sequence is drawn uniformly at random from all such sequences. Everyone who has selected the same 4 numbers in order as the winning sequence wins the lottery.

(a) What is the probability of winning?

I don't quite understand the question, but is it right to do
1/10 * 1/9 * 1/8 * 1/7 ???

(b)What is the expected return assuming tickets costs 2 dollars and the prize for winning is $100?

how do I do this???