Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.

Ex Input:
Problem: if a man lost 8 % by selling oranges at the rate of 25 a rupee at how many a rupee must he sell them to gain 25 % ?
Options: a. 20, b. 15, c. 18.4, d. 20, e. 12.8

Ex Output:
c

Ex Input:
Problem: a shopkeeper buys mangoes at the rate of 5 a rupee and sells them at 2 a rupee. find his net profit or loss percent ?
Options: a. 34 %, b. 30 %, c. 50 %, d. 150 %, e. 33 %

Ex Output:
d

Ex Input:
Problem: the perimeter of a square is equal to the perimeter of a rectangle of length 19 cm and breadth 14 cm. find the circumference of a semicircle whose diameter is equal to the side of the square. ( round off your answer to two decimal places )
Options: a. 22.78, b. 23.54, c. 23.5, d. 24.55, e. 25.93

Ex Output:
e