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: in a factory, an average of 60 tv ' s are produced per day for the fist 25 days of the months. a few workers fell ill for the next 5 days reducing the daily avg for the month to 58 sets / day. the average production per day for day last 5 days is ?
Options: a. 20, b. 36, c. 48, d. 50, e. 59

Ex Output:
c


Ex Input:
Problem: if john makes a contribution to a charity fund at school, the average contribution size will increase by 50 % reaching $ 75 per person. if there were 1 other contributions made before john ' s, what is the size of his donation ?
Options: a. $ 100, b. $ 150, c. $ 200, d. $ 250, e. $ 450

Ex Output:
a


Ex Input:
Problem: if m = 3 ^ n, what is the greatest value of n for which m is a factor of 31 !
Options: a. 8, b. 10, c. 12, d. 14, e. 16

Ex Output:

d