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 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: if the average of 5 positive integers is 50 and the difference between the largest and the smallest of these 5 numbers is 10, what is the maximum value possible for the largest of these 5 integers ?
Options: a. 50, b. 58, c. 49, d. 48, e. 44

Ex Output:
b


Ex Input:
Problem: how many positive integers less than 70 have a reminder 01 when divided by 3 ?
Options: a. 13, b. 24, c. 35, d. 16, e. 17

Ex Output:

b