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: in an examination it is necessary for a candidate to get 45 % of the maximum marks to pass . a candidate who gets 180 marks , fails by 45 marks . find the maximum marks . 
Options: a ) 450 , b ) 600 , c ) 500 , d ) 550 , e ) 650
Example Output: c

Example Input: Problem: at what rate percent per annum will the simple interest on a sum of money be 2 / 5 of the amount in 10 years ? 
Options: a ) 4 % , b ) 74 % , c ) 64 % , d ) 74 % , e ) 94 %
Example Output: a

Example Input: Problem: if the price of an article went up by 25 % , then by what percent should it be brought down to bring it back to its original price ? 
Options: a ) 20 % , b ) 2 / 8 % , c ) 2 / 1 % , d ) 1 / 3 % , e ) 2 / 7 %
Example Output:
a