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 compound interest and simple interest on a certain amount of money at 5 % per annum for 2 years is 17 . find the sum :
Options: a ) 4500 , b ) 7500 , c ) 5000 , d ) 6800 , e ) none of these
Example Output: d

Example Input: Problem: a man has $ 10,000 to invest . he invests $ 4000 at 5 % and $ 3500 at 4 % . in order to have a yearly income of $ 500 , he must invest the remainder at :
Options: a ) 4.6 % , b ) 3.6 % , c ) 6.4 % , d ) 7.8 % , e ) 8.9 %
Example Output: c

Example Input: Problem: a scuba diver descends at a rate of 60 feet per minute . a diver dive from a ship to search for a lost ship at the depth of 3600 feet below the sea level . . how long will he take to reach the ship ?
Options: a ) 60 minutes , b ) 72 minutes , c ) 75 minutes , d ) 76 minutes , e ) 77 minutes
Example Output:
a