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: x does a work in 20 days. y does the same work in 40 days. in how many days they together will do the same work ?
Options: a. 10, b. 12, c. 20, d. 30, e. 13.33

Ex Output:
e


Ex Input:
Problem: 50 % of a number is more than 40 % of 120 by 180. find the number ?
Options: a. 456, b. 480, c. 420, d. 445, e. 320

Ex Output:
a


Ex Input:
Problem: maxwell leaves his home and walks toward brad ' s house at the same time that brad leaves his home and runs toward maxwell ' s house. if the distance between their homes is 72 kilometers, maxwell ' s walking speed is 6 km / h, and brad ' s running speed is 12 km / h. what is the distance traveled by maxwell when they meet in the middle ?
Options: a. 14, b. 24, c. 16, d. 18, e. 20

Ex Output:

b