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: a statue is being carved by a sculptor. the original piece of marble weighed 180 kg. in the first week 28 percent is cut away. in the second week 18 percent of the remainder is cut away. in the third week the statue is completed when 20 percent of the remainder is cut away. what is the weight of the final statue ?
Options: a. 105 kg, b. 85 kg, c. 108 kg, d. 125 kg, e. 117 kg

Ex Output:
b


Ex Input:
Problem: a fort had provision of food for 150 men for 45 days. after 15 days, 10 men left the fort. the number of days for which the remaining food will last, is :
Options: a. 32, b. 37 1 / 4, c. 42, d. 54, e. 45

Ex Output:
a


Ex Input:
Problem: a set of pictures of butterflies contains 10 pictures. jim bought 3 of the pictures. if 2 pictures are to be picked out from the 10 pictures, what is the probability that both pictures are not those that were already bought by jim ?
Options: a. 14 / 15, b. 3 / 5, c. 6 / 13, d. 7 / 15, e. 7 / 10

Ex Output:

d