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 speed of the boat in still water in 12 kmph. it can travel downstream through 54 kms in 3 hrs. in what time would it cover the same distance upstream ?
Options: a. 8 hours, b. 6 hours, c. 4 hours, d. 5 hours, e. 9 hours

Ex Output:
e

Ex Input:
Problem: the smallest number which when diminished by 2, is divisible by 12, 16, 18, 21 and 28 is
Options: a. 1008, b. 1010, c. 1022, d. 1032, e. 1043

Ex Output:
b

Ex Input:
Problem: a and b are two multiples of 14, and q is the set of consecutive integers between a and b, inclusive. if q contains 12 multiples of 14, how many multiples of 7 are there in q ?
Options: a. 20, b. 21, c. 22, d. 23, e. 24

Ex Output:
d