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: what is the smallest positive integer x such that 66 - x is the cube of a positive integer
Options: a. 5, b. 7, c. 47, d. 9, e. 2

Ex Output:
e

Ex Input:
Problem: 10 ^ ( 600 ) a 10 ^ ( 580 ) = ?
Options: a. 10 ^ 10, b. 10 ^ 20, c. 10 ^ 22, d. 10 ^ 23, e. 10 ^ 24

Ex Output:
b

Ex Input:
Problem: 0.0008 ? = 0.02
Options: a. 40, b. 4, c. 0.4, d. none of these, e. 0.04

Ex Output:
e