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: the sum of 4 consecutive even numbers is 140. what would be the smallest number ?
Options: a. 32, b. 88, c. 70, d. 123, e. 12

Ex Output:
a


Ex Input:
Problem: two trains of equal length are running on parallel lines in the same directions at 46 km / hr. and 36 km / hr. the faster trains pass the slower train in 72 seconds. the length of each train is :
Options: a. 82 m, b. 50 m, c. 72 m, d. 100 m, e. none of these

Ex Output:
d


Ex Input:
Problem: if 5 x = 3 y and xy ≠ 0, what is the ratio of 1 / 5 * x to 1 / 6 * y ?
Options: a. 25 / 6, b. 36 / 25, c. 18 / 25, d. 5 / 6, e. 25 / 36

Ex Output:

c