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: find the compound interest on $ 20000 in 2 years at 4 % per annum , the interest being compounded half - yearly ? 
Options: a ) $ 645.56 , b ) $ 1648.64 , c ) $ 954.26 , d ) $ 745.69 , e ) $ 1020.45
Example Output: b

Example Input: Problem: to produce an annual income of rs . 800 from a 8 % stock at 90 , what is the amount of stock needed ? 
Options: a ) 10000 , b ) 11000 , c ) 12000 , d ) 13000 , e ) 14000
Example Output: a

Example Input: Problem: the price of an item is discounted 10 percent on day 1 of a sale . on day 2 , the item is discounted another 10 percent , and on day 3 , it is discounted an additional 25 percent . the price of the item on day 3 is what percentage of the sale price on day 1 ? 
Options: a ) 28 % , b ) 67.5 % , c ) 64.8 % , d ) 70 % , e ) 72 %
Example Output:
b