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: in a certain math department , students are required to enroll in either calculus or trigonometry , each of which is offered in beginner and advanced courses . the number of students enrolled in trigonometry is 50 % greater than the number of students enrolled in calculus , and 80 % of calculus students are enrolled in the beginner course . if 4 / 5 of students are in the beginner courses , and one student is selected at random , what is the probability that an advanced trigonometry student is selected ? 
Options: a ) 8 % , b ) 12 % , c ) 16 % , d ) 20 % , e ) 24 %
Example Output: b

Example Input: Problem: a sum of $ 1000 amounts to $ 1500 in 5 years at simple interest . if the interest rate is increased by 5 % it would amount to how much ? 
Options: a ) $ 1000 , b ) $ 750 , c ) $ 1541 , d ) $ 1478 , e ) $ 1750
Example Output: e

Example Input: Problem: a trader bought a car at 25 % discount on its original price . he sold it at a 40 % increase on the price he bought it . what percent of profit did he make on the original price ? 
Options: a ) 118 , b ) 110 , c ) 105 , d ) 113 , e ) 115
Example Output:
c