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: a man can row upstream at 25 kmph and downstream at 55 kmph, and then find the speed of the man in still water ?
Options: a. 65, b. 40, c. 30, d. 78, e. 38

Ex Output:
b


Ex Input:
Problem: find the value o f 72519 x 9999 = m ?
Options: a. 434539873, b. 355797990, c. 435453490, d. m = 725117481, e. 873430134

Ex Output:
d


Ex Input:
Problem: an agent, gets a commission of 2.5 % on the sales of cloth. if on a certain day, he gets rs. 21 as commission, the cloth sold through him on that day is worth
Options: a. 333, b. 500, c. 840, d. 299, e. 132

Ex Output:

c