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 particular library has 75 books in a special collection , all of which were in the library at the beginning of the month . these book are occasionally loaned out through an inter - library program . if , by the end of the month , 60 percent of books that were loaned out are returned and there are 65 books in the special collection at that time , how many books of the special collection were loaned out during that month ? 
Options: a ) 20 , b ) 25 , c ) 35 , d ) 40 , e ) 55
Example Output: b

Example Input: Problem: in how many years will a sum of money doubles itself at 12 % per annum on simple interest ? 
Options: a ) 15 % , b ) 20 % , c ) 10 % , d ) 8 % , e ) 22 %
Example Output: d

Example Input: Problem: the present worth of rs . 845 due in 2 years at 4 % per annum compound interest is 
Options: a ) rs . 150.50 , b ) rs . 154.75 , c ) rs . 781.25 , d ) rs . 158 , e ) none
Example Output:
c