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: ramesh purchased a refrigerator for rs. 12500 after getting a discount of 20 % on the labelled price. he spent rs. 125 on transport and rs. 250 on installation. at what price should it be sold so that the profit earned would be 18 % if no discount was offered ?
Options: a. 17608, b. 17606, c. 17604, d. 17600, e. 18880

Ex Output:
e

Ex Input:
Problem: a man swims downstream 36 km and upstream 18 km taking 3 hours each time, what is the speed of the man in still water ?
Options: a. 7, b. 8, c. 9, d. 2, e. 4

Ex Output:
c

Ex Input:
Problem: 5 years ago, paula was 3 times as old as karl. in 6 years, paula will be twice as old as karl. what is the sum of their ages now ?
Options: a. 42, b. 46, c. 50, d. 54, e. 58

Ex Output:
d