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: a batsman makes a score of 87 runs in the 17 th inning and thus increases his average by 3. find his average after 17 th inning.
Options: a. 39, b. 88, c. 26, d. 87, e. 11

Ex Output:
a

Ex Input:
Problem: there are 27 different 3 - digit integers that can be formed using only the digits 3, 4 and 5. if all 27 of the integers were listed, what would their sum be ?
Options: a. 11,888, b. 11,988, c. 12,088, d. 12,188, e. 12,288

Ex Output:
b

Ex Input:
Problem: a certain rectangular crate measures 8 feet by 14 feet by 16 feet. a cylindrical gas tank is to be made for shipment in the crate and will stand upright when the crate is placed on one of its six faces. what should the radius of the tank be if it is to be of the largest possible volume ?
Options: a. 4, b. 5, c. 6, d. 8, e. 10

Ex Output:
c