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: a man has $ 10,000 to invest . he invests $ 4000 at 5 % and $ 3500 at 4 % . in order to have a yearly income of $ 500 , he must invest the remainder at :
Options: a ) 4.6 % , b ) 3.6 % , c ) 6.4 % , d ) 7.8 % , e ) 8.9 %

Ex Output:
c

Ex Input:
Problem: in a certain pond , 40 fish were caught , tagged , and returned to the pond . a few days later , 40 fish were caught again , of which 2 were found to have been tagged . if the percent of tagged fish in the second catch approximates the percent of tagged fish in the pond , what is the approximate number of fish in the pond ?
Options: a ) 1000 , b ) 625 , c ) 1,250 , d ) 2,500 , e ) 10,000

Ex Output:
a

Ex Input:
Problem: a company pays 15.5 % dividend to its investors . if an investor buys rs . 50 shares and gets 25 % on investment , at what price did the investor buy the shares ?
Options: a ) 25 , b ) 31 , c ) 18 , d ) 19 , e ) 01

Ex Output:
b