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: if a lends rs . 2000 to b at 15 % per annum and b lends the same sum to c at 17 % per annum then the gain of b in a period of 4 years is ? 
Options: a ) 155 , b ) 162 , c ) 157.5 , d ) 160 , e ) 157.12
Example Output: d

Example Input: Problem: by selling 16 pens for a rupee a woman loses 5 % . how many for a rupee should he sell in order to gain 18 % ? 
Options: a ) 12 , b ) 14 , c ) 45 , d ) 13 , e ) 65
Example Output: d

Example Input: Problem: a sum of money at simple interest amounts to rs . 815 in 3 years and to rs . 854 in 4 years . the sum is : 
Options: a ) rs . 650 , b ) rs . 690 , c ) rs . 698 , d ) rs . 700 , e ) rs . 740
Example Output:
c