Provide your best answer for the following math problem. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The problem is: if the selling price of 50 articles is equal to the cost price of 30 articles , then the loss or gain percent is :
40 %
The given information is not sufficient to determine the loss or gain percent.