Instructions: In this task, you need to answer the given multiple-choice question on the gain. Gain is the value by which to multiply the input. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.
Input: Problem: if the cost price of 50 articles is equal to the selling price of 28 articles , then the gain or loss percent is ? 
Options: a ) 22 , b ) 65 , c ) 78.57 , d ) 33 , e ) 25
Output:
c