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: 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

Ex Output:
c


Ex Input:
Problem: ( ( - 1.9 ) ( 0.6 ) – ( 2.6 ) ( 1.2 ) ) / 2.0 = ?
Options: a. - 0.71, b. - 2.13, c. 1.07, d. 1.71, e. 2.71

Ex Output:
b


Ex Input:
Problem: at a certain fruit stand, the price of each apple is 40 cents and the price of each orange is 60 cents. mary selects a total of 30 apples and oranges from the fruit stand, and the average ( arithmetic mean ) price of the 30 pieces of fruit is 56 cents. how many oranges must mary put back so that the average price of the pieces of fruit that she keeps is 52 cents ?
Options: a. 10, b. 11, c. 13, d. 14, e. 15

Ex Output:

e