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'.

Example Input: Problem: some of 10 % - intensity red paint is replaced with 20 % solution of red paint such that the new paint intensity is 15 % . what fraction of the original paint was replaced ? 
Options: a ) 2 / 5 , b ) 2 / 3 , c ) 1 / 2 , d ) 1 / 3 , e ) 1 / 5
Example Output: c

Example Input: Problem: the banker â € ™ s discount of a certain sum of money is rs . 42 and the true discount on the same sum for the same time is rs . 36 . the sum due is 
Options: a ) 252 , b ) 280 , c ) 360 , d ) 450 , e ) none
Example Output: a

Example Input: Problem: a person buys an article at rs . 500 . at what price should he sell the article so as to make a profit of 25 % ? 
Options: a ) 600 , b ) 887 , c ) 625 , d ) 654 , e ) 712
Example Output:
c