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: reena took a loan of $ . 1200 with simple interest for as many years as the rate of interest . if she paid $ 588 as interest at the end of the loan period , what was the rate of interest ? 
Options: a ) 3.6 , b ) 7 , c ) 18 , d ) can not be determined , e ) none of these
Example Output: b

Example Input: Problem: if the simple interest on a certain amount in at 4 % rate 5 years amounted to rs . 2080 less than the principal . what was the principal ? 
Options: a ) 1500 , b ) 2600 , c ) 2507 , d ) 3200 , e ) 11500
Example Output: b

Example Input: Problem: a sum fetched a total simple interest of rs . 100 at the rate of 5 p . c . p . a . in 4 years . what is the sum ? 
Options: a ) 800 , b ) 600 , c ) 500 , d ) 1000 , e ) 300
Example Output:
c