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: sakshi can do a piece of work in 5 days. tanya is 25 % more efficient than sakshi. the number of days taken by tanya to do the same piece of work :
Options: a. 4, b. 16, c. 18, d. 25, e. 10
Example Output: a

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: a is two years older than b who is twice as old as c. if the total of the ages of a, b nd c be 27, then how old is b ?
Options: a. 7, b. 8, c. 9, d. 10, e. 11
Example Output:
d