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: rs . 6000 is lent out in two parts . one part is lent at 5 % p . a simple interest and the other is lent at 10 % p . a simple interest . the total interest at the end of one year was rs . 450 . find the ratio of the amounts lent at the lower rate and higher rate of interest ? 
Options: a ) 5 : 1 , b ) 5 : 5 , c ) 5 : 8 , d ) 5 : 4 , e ) 5 : 2
Example Output: b

Example Input: Problem: ritesh and co . generated revenue of rs . 1,500 in 2006 . this was 12.5 % of its gross revenue . in 2007 , the gross revenue grew by rs . 2,500 . what is the percentage increase in the revenue in 2007 ? 
Options: a ) 12.5 % , b ) 20.83 % , c ) 25 % , d ) 50 % , e ) none of these
Example Output: b

Example Input: Problem: a money lender lent rs . 1000 at 3 % per year and rs . 1200 at 5 % per year . the amount should be returned to him when the total interest comes to rs . 350 . find the number of years . 
Options: a ) 3.5 , b ) 3.75 , c ) 3.88 , d ) 4.25 , e ) 4.5
Example Output:
c