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: a , b and c enter into partnership . a invests some money at the beginning , b invests double the amount after 6 months , and c invests thrice the amount after 8 months . if the annual gain be rs . 21000 . a ' s share is ? 
Options: a ) 2999 , b ) 2778 , c ) 7000 , d ) 2889 , e ) 6612
Example Output: c

Example Input: Problem: a can complete a certain job in 19 days . b is 90 % more efficient than a . in how many days can b complete the same job ? 
Options: a ) 6 , b ) 6.25 , c ) 7 , d ) 7.5 , e ) 10
Example Output: e

Example Input: Problem: at what rate percent per annum will the simple interest on a sum of money be 3 / 5 of the amount in 10 years ? 
Options: a ) 6 % , b ) 7 % , c ) 9 % , d ) 3 % , e ) 1 %
Example Output:
a