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: reena took a loan of $ . 1200 with simple interest for as many years as the rate of interest . if she paid $ 588 as interest at the end of the loan period , what was the rate of interest ? 
Options: a ) 3.6 , b ) 7 , c ) 18 , d ) can not be determined , e ) none of these
Example Output: b

Example Input: Problem: running at the same constant rate , 6 identical machines can produce a total of 270 bottles per minute . at this rate , how many bottles could 8 such machines produce in 4 minutes ? 
Options: a ) 648 , b ) 1800 , c ) 2700 , d ) 1440 , e ) none of these
Example Output: d

Example Input: Problem: a retailer purchases shirts from a wholesaler and then sells the shirts in her store at a retail price that is 70 percent greater than the wholesale price . if the retailer decreases the retail price by 30 percent this will have the same effect as increasing the wholesale price by what percent ? 
Options: a ) 26 , b ) 37.5 , c ) 42 , d ) 19 , e ) 50
Example Output:
d