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: if difference between compound interest and simple interest on a sum at 10 % p . a . for 2 years is rs . 150 then sum is 
Options: a ) s . 15000 , b ) s . 15100 , c ) s . 15800 , d ) s . 16000 , e ) s . 16200
Example Output: a

Example Input: Problem: a company recently conducted a survey and found that 25,000 of its customers live in rural areas . if the number of customers who live in urban areas is 120 percent greater than the number of customers who live in rural areas , how many customers live in urban areas ? 
Options: a ) 50,000 , b ) 55,000 , c ) 60,000 , d ) 65,000 , e ) 70,000
Example Output: b

Example Input: Problem: running at the same constant rate , 6 identical machines can produce a total of 240 bottles per minute . at this rate , how many bottles could 10 such machines produce in 4 minutes ? 
Options: a ) 648 , b ) 1,800 , c ) 1,600 , d ) 10,800 , e ) 64,800
Example Output:
c