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: alex takes a loan of $ 5,000 to buy a used truck at the rate of 2 % simple interest . calculate the annual interest to be paid for the loan amount . 
Options: a ) 100 , b ) 150 , c ) 720 , d ) 200 , e ) 750
Example Output: a

Example Input: Problem: population of a city in 20004 was 1000000 . if in 2005 there isan increment of 15 % , in 2006 there is a decrements of 35 % and in 2007 there is an increment of 30 % , then find the population of city atthe end of the year 2007 
Options: a ) 976374 , b ) 971750 , c ) 980241 , d ) 2356677 , e ) 1083875
Example Output: b

Example Input: Problem: what quantity of water should taken out to concentrate 12 liters of 40 % acidic liquid to 60 % acidic liquid ? 
Options: a ) 4 liters , b ) 10 liters , c ) 15 liters , d ) 8 liters , e ) 6 liters
Example Output:
a