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: find the sum of first 89 odd numbers
Options: a. 7921, b. 4800, c. 7900, d. 4980, e. 4960

Ex Output:
a


Ex Input:
Problem: the mean proportional between 4 and 16 is ?
Options: a. 12, b. 13, c. 14, d. 15, e. 16

Ex Output:
e


Ex Input:
Problem: the length of a side of a hexagon is 7 inches. what is the perimeter ?
Options: a. 48, b. 42, c. 44, d. 45, e. 40

Ex Output:

b