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 difference between c . i . and s . i . on an amount of rs . 15,000 for 2 years is rs . 24 . what is the rate of interest per annum ?
Options: a ) 8 , b ) 2 , c ) 9 , d ) 4 , e ) 6
Example Output: d

Example Input: Problem: shawn invested one half of his savings in a bond that paid simple interest for 2 years and received $ 550 as interest . he invested the remaining in a bond that paid compound interest , interest being compounded annually , for the same 2 years at the same rate of interest and received $ 605 as interest . what was the value of his total savings before investing in these two bonds ?
Options: a ) $ 2,750 , b ) $ 5,500 , c ) $ 11,000 , d ) $ 22,000 , e ) $ 44,000
Example Output: a

Example Input: Problem: by selling 100 pens , a trader gains the cost of 30 pens . find his gain percentage ?
Options: a ) 30 % , b ) 33 % , c ) 31 % , d ) 32 % , e ) 34 %
Example Output:
a