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: 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
Example Output: b

Example Input: Problem: the sum of 4 consecutive even numbers is 140. what would be the smallest number ?
Options: a. 32, b. 88, c. 70, d. 123, e. 12
Example Output: a

Example Input: Problem: in one hour, a boat goes 11 km along the stream and 5 km against the stream. the speed of the boat in still water is :
Options: a. 3, b. 5, c. 8, d. 9, e. 10
Example Output:
c