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: if 5 a = 3125, then the value of 5 ( a - 3 ) is :
Options: a. 25, b. 125, c. 625, d. 1625, e. none of these
Example Output: a

Example Input: Problem: last year elaine spent 20 % of her annual earnings on rent. this year she earned 35 % more than last year and she spent 30 % of her annual earnings on rent. the amount she spent on rent this year is what percent of the amount spent on rent last year ?
Options: a. 202.5, b. 194.5, c. 197.5, d. 182.5, e. 177.5
Example Output: a

Example Input: Problem: when working alone, painter w can paint a room in 2 hours, and working alone, painter x can paint the same room in z hours. when the two painters work together and independently, they can paint the room in 3 / 4 of an hour. what is the value of z ?
Options: a. 3 / 4, b. 1 [ 1 / 5 ], c. 1 [ 2 / 5 ], d. 1 [ 3 / 4 ], e. 2
Example Output:
b