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: 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

Ex Output:
c


Ex Input:
Problem: what is the area of a regular hexagon with sides 1 in. long ?
Options: a. 1.59 square inch, b. 2.59 square inch, c. 3.59 square inch, d. 4.59 square inch, e. 2.69 square inch

Ex Output:
b


Ex Input:
Problem: a train 250 m long running at 72 kmph crosses a platform in 25 sec. what is the length of the platform ?
Options: a. 150 m, b. 200 m, c. 250 m, d. 270 m, e. 300 m

Ex Output:

c