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.

Input: Consider Input: Problem: an engine moves at the speed of 30 kmph without any coaches attached to it. speed of the train reduces at the rate that varies directly as the square root of the number of coaches attached. when 9 coaches are attached speed decreases to 18 kmph. what will be the speed of train when 16 coaches are attached.
Options: a. 14, b. 16, c. 18, d. 20, e. 22

Output: a

Input: Consider Input: Problem: in 5 football games thus far this season, barry has run for 98, 107, 85, 89, and 91 yards. at a minimum, how many yards m will he need to gain this sunday if he wants to keep his season average above 100 yards ?
Options: a. 101, b. 116, c. m = 130, d. m = 131, e. m = 141

Output: d

Input: Consider Input: Problem: a certain mixture of nuts consists of 5 parts almonds to 2 parts walnuts, by weight. what is the number of pounds of almonds in 280 pounds of the mixture ?
Options: a. 200, b. 84, c. 40, d. 28, e. 20
Output: a