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: tickets to a certain concert sell for $ 20 each . the first 10 people to show up at the ticket booth received a 40 % discount , and the next 20 received a 15 % discount . if 50 people bought tickets to the concert , what was the total revenue from ticket sales ? 
Options: a ) $ 600 , b ) $ 740 , c ) $ 860 , d ) $ 980 , e ) $ 1,140
Example Output: c

Example Input: Problem: i sold a book at a profit of 10 % . had i sold it for $ 150 more , 15 % would have been gained . find the cost price ? 
Options: a ) $ 2000 , b ) $ 2500 , c ) $ 3000 , d ) $ 3120 , e ) $ 1540
Example Output: c

Example Input: Problem: the cost price of a radio is rs . 2400 and it was sold for rs . 2100 , find the loss % ? 
Options: a ) 12.5 % , b ) 11 % , c ) 13 % , d ) 15 % , e ) 12.8 %
Example Output:
a