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 certain protective additive increases from 50 days to 60 days the time between required maintenance checks on an industrial vehicle. by what percent is the time between maintenance checks increased by using the additive ?
Options: a. 25 %, b. 33 1 / 3 %, c. 50 %, d. 66 2 / 3 %, e. 20 %
Example Output: e

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: the cross section of a canal is trapezium in shape. the canal is 12 m wide at the top and 8 m wide at the bottom. if the area of the cross section is 840 sq. m, the depth of the canal is :
Options: a. 42 m, b. 84 m, c. 63 m, d. 8.75 m, e. 9.75 m
Example Output:
b