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: 40 is subtracted from 60 % of a number, the result is 50. find the number ?
Options: a. 150, b. 330, c. 277, d. 279, e. 712

Ex Output:
a

Ex Input:
Problem: find the maximum value of the function f ( x ) = x 5 if x is a number between - 5 and 13.
Options: a. 6, b. 7, c. 8, d. 9, e. none

Ex Output:
c

Ex Input:
Problem: a train covers a distance of 100 km in 1 hour. if its speed is decreased by 10 km / hr, the time taken by the car to cover the same distance will be ?
Options: a. 1 hr, b. 1 hr 6 min, c. 50 min, d. 1 hr 30 min, e. 1 hr 45 min

Ex Output:
b