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.

Example Input: Problem: a monkey ascends a greased pole 10 meters high. he ascends 2 meters in the first minute and then slips down 1 meter in the alternate minute. if this pattern continues until he climbs the pole, in how many minutes would he reach at the top of the pole ?
Options: a. 10 th minute, b. 21 st minute, c. 17 th minute, d. 22 nd minute, e. 13 th minute
Example Output: c

Example 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
Example Output: e

Example Input: Problem: a man can row upstream at 25 kmph and downstream at 31 kmph, and then find the speed of the man in still water ?
Options: a. 22, b. 28, c. 30, d. 27, e. 18
Example Output:
b