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: cereal a is 10 % sugar by weight, whereas healthier but less delicious cereal b is 2 % sugar by weight. to make a delicious and healthy mixture that is 3 % sugar, what should be the ratio of cereal a to cereal b, by weight ?
Options: a. 2: 9, b. 2: 7, c. 1: 7, d. 1: 4, e. 1: 3
Example Output: c

Example Input: Problem: jerome anticipated that the webweb. com stock price would fall and sold all his webweb. com stocks for $ 5 per stock. he paid $ 10,000 tax on the revenue. a week later, jerome became convinced that the webweb. com stock price would rise, and he used the money that he had gotten from selling the webweb. com stocks to purchase them again, this time at $ 6 per stock. if jerome ended up having 7000 webweb. com stocks fewer than the number he had before selling them, how many webweb. com stocks did he have originally ?
Options: a. 10,000, b. 11,600, c. 17,000, d. 14,000, e. 16,400
Example Output: c

Example Input: Problem: a fair 2 sided coin is flipped 7 times. what is the probability that tails will be the result at least twice, but not more than 7 times ?
Options: a. 119 / 128, b. 120 / 113, c. 114 / 210, d. 121 / 141, e. 104 / 117
Example Output:
a