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 x and y are positive integers and 3 + x + y + xy = 17, what is the value of x + y ?
Options: a. 3, b. 5, c. 6, d. 8, e. 9
Example Output: c

Example Input: Problem: by selling 15 pencils for a rupee a man loses 20 %. how many for a rupee should he sell in order to gain 20 % ?
Options: a. 8, b. 7, c. 6, d. 4, e. 10
Example Output: e

Example Input: Problem: positive integer y is 50 percent of 50 percent of positive integer x, and y percent of x equals 100. what is the value of y ?
Options: a. 50, b. 100, c. 200, d. 1,000, e. 2,000
Example Output:
a