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: by selling 15 pencils for a rupee a man loses 20 %. how many for a rupee should he sell in order to gain 20 % ?
Options: a. 8, b. 7, c. 6, d. 4, e. 10

Output: e


Input: Consider Input: Problem: a company recently conducted a survey and found that 20,000 of its customers live in rural areas. if the number of customers who live in urban areas is 100 percent greater than the number of customers who live in rural areas, how many customers live in urban areas ?
Options: a. 40,000, b. 45,000, c. 50,000, d. 55,000, e. 60,000


Output: a