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 sum of money at simple interest amounts to $ 815 in 3 years and to $ 854 in 4 years . the sum is : 
Options: a ) $ 153 , b ) $ 698 , c ) $ 398 , d ) $ 549 , e ) $ 675
Example Output: b

Example Input: Problem: what annual payment will discharge a debt of rs . 1030 due in 2 years at the rate of 5 % compound interest ? 
Options: a ) 553.94 , b ) 551.25 , c ) 534.33 , d ) 543.33 , e ) 646.33
Example Output: a

Example Input: Problem: there is 60 % increase in an amount in 6 years at si . what will be the ci of rs . 13,000 after 3 years at the same rate ? 
Options: a ) 2372 , b ) 2572 , c ) 4303 , d ) 2343 , e ) 3972
Example Output:
c