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'.

Ex Input:
Problem: walking 7 / 6 of his usual rate , a boy reaches his school 3 min early . find his usual time to reach the school ?
Options: a ) 21 , b ) 28 , c ) 99 , d ) 77 , e ) 66

Ex Output:
a

Ex Input:
Problem: a reduction of 40 % in the price of bananas would enable a man to obtain 64 more for rs . 40.00001 , what is reduced price per dozen ?
Options: a ) 6 , b ) 5 , c ) 4 , d ) 3 , e ) 2

Ex Output:
d

Ex Input:
Problem: jackie has two solutions that are 2 percent sulfuric acid and 12 percent sulfuric acid by volume , respectively . if these solutions are mixed in appropriate quantities to produce 60 liters of a solution that is 5 percent sulfuric acid , approximately how many liters of the 12 percent solution will be required ?
Options: a ) 18 , b ) 20 , c ) 24 , d ) 36 , e ) 42

Ex Output:
a