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.

Example 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
Example Output: a

Example Input: Problem: a shopkeeper sells 500 metres of cloth for rs. 18000 at a loss of rs. 5 per metre. find his cost price for one metre of cloth ?
Options: a. 12, b. 27, c. 29, d. 50, e. 41
Example Output: e

Example Input: Problem: if w / x = 1 / 3 and w / y = 3 / 4, then ( x + y ) / y =
Options: a. 13 / 4, b. 6 / 5, c. 7 / 5, d. 8 / 5, e. 9 / 5
Example Output:
a