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 72 articles is equal to the selling price of 60 articles , then what is the percent profit ? 
Options: a ) 10 % , b ) 15 % , c ) 20 % , d ) 25 % , e ) 30 %
Output:
c