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: there is one 4 - digit whole number n, such that the last 4 digits of n 2 are in fact the original number n
Options: a. 8476, b. 7376, c. 9376, d. 7378, e. 9466
Example Output: c

Example Input: Problem: a light flashes every 30 seconds, how many times will it flash in ? of an hour ?
Options: a. 550, b. 600, c. 650, d. 700, e. 120
Example Output: e

Example Input: Problem: if 3 workers collect 48 kg of cotton in 4 days, how many kg of cotton will 9 workers collect in 2 days ?
Options: a. 88 kg, b. 65 kg, c. 72 kg, d. 44 kg, e. 55 kg
Example Output:
c