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: the present worth of rs . 2310 due years hence , the rate of interest being 15 % per annum , is : 
Options: a ) rs . 1440 , b ) rs . 1750 , c ) rs . 1680 , d ) rs . 1840 , e ) none of these
Example Output: c

Example Input: Problem: the price of a book is increased from $ 300 to $ 480 . what is the % of increase in its price ? 
Options: a ) 10 % , b ) 20 % , c ) 40 % , d ) 50 % , e ) 60 %
Example Output: e

Example Input: Problem: a sum of money deposited at c . i . amounts to rs . 2420 in 2 years and to rs . 3025 in 3 years . find the rate percent ? 
Options: a ) 11 , b ) 10 , c ) 28 , d ) 25 , e ) 82
Example Output:
d