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: kathleen can paint a room in 4 hours, and anthony can paint an identical room in 5 hours. how many hours would it take kathleen and anthony to paint both rooms if they work together at their respective rates ?
Options: a. 8 / 15, b. 40 / 9, c. 15 / 8, d. 9 / 4, e. 15 / 4

Ex Output:
b


Ex Input:
Problem: the least number which when divided by 5, 6, 7 and 8 leaves a remainder 3, but when divided by 9 leaves no remainder, is :
Options: a. 2377, b. 1683, c. 2677, d. 9972, e. 1611

Ex Output:
b


Ex Input:
Problem: ritesh and co. generated revenue of rs. 1,600 in 2006. this was 12.5 % of its gross revenue. in 2007, the gross revenue grew by rs. 2,500. what is the percentage increase in the revenue in 2007 ?
Options: a. 12.5 %, b. 19.53 %, c. 25 %, d. 50 %, e. none of these

Ex Output:

b