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: there are 15 boys and 10 girls in a class. if three students are selected at random, in how many ways that 1 girl or 2 boys are selected ?
Options: a. 100, b. 105, c. 115, d. 120, e. 125
Example Output: c

Example Input: Problem: when positive integer n is divided by 3, the remainder is 1. when n is divided by 7, the remainder is 5. what is the smallest positive integer k such that k + n is a multiple of 21 ?
Options: a. 2, b. 4, c. 6, d. 8, e. 10
Example Output: a

Example Input: Problem: having received his weekly allowance, john spent 3 / 5 of his allowance at the arcade. the next day he spent one third of his remaining allowance at the toy store, and then spent his last $ 0.88 at the candy store. what is john ’ s weekly allowance ?
Options: a. $ 2.70, b. $ 3.00, c. $ 3.30, d. $ 3.60, e. $ 3.90
Example Output:
c