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 tens digit of 6 ^ 10 ?
Options: a. 7, b. 3, c. 5, d. 1, e. 9

Ex Output:
a


Ex Input:
Problem: the area of one square is x ^ 2 + 4 x + 4 and the area of another square is 4 x ^ 2 − 12 x + 9. if the sum of the perimeters of both squares is 32, what is the value of x ?
Options: a. 0, b. 2, c. 2.5, d. 4.67, e. 3

Ex Output:
e


Ex Input:
Problem: if the simple interest on a certain amount in at 4 % rate 5 years amounted to rs. 2240 less than the principal. what was the principal ?
Options: a. 1500, b. 2500, c. 2507, d. 2800, e. 11500

Ex Output:

d