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: what is the compound interest on rs : 40,000 for 4 months at the rate of 5 % per annum
Options: a ) 670.85 , b ) 671.85 , c ) 672.85 , d ) 673.85 , e ) 674.85
Example Output: a

Example Input: Problem: a grocer has 400 pounds of coffee in stock , 25 percent of which is decaffeinated . if the grocer buys another 100 pounds of coffee of which 60 percent is decaffeinated , what percent , by weight , of the grocer ' s stock of coffee is decaffeinated ?
Options: a ) 28 % , b ) 30 % , c ) 32 % , d ) 34 % , e ) 40 %
Example Output: c

Example Input: Problem: a sum of 14,800 amounts to 19,800 in 3 years at the rate of simple interest . what is the rate of interest ?
Options: a ) 12 % , b ) 11 % , c ) 16 % , d ) 15 % , e ) 18 %
Example Output:
b