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: find the cost of fencing around a circular field of diameter 32 m at the rate of rs. 2 a meter ?
Options: a. 201, b. 132, c. 772, d. 592, e. 261
Example Output: a

Example Input: Problem: in a certain deck of cards, each card has a positive integer written on it, in a multiplication game a child draws a card and multiplies the integer on the card with the next large integer. if the each possible product is between 10 and 400, then the least and greatest integer on the card would be
Options: a. 3 and 15, b. 3 and 20, c. 4 and 13, d. 4 and 14, e. 5 and 14
Example Output: b

Example Input: Problem: pipe a can fill a tank in 6 hours. due to a leak at the bottom, it takes 12 hours for the pipe a to fill the tank. in what time can the leak alone empty the full tank ?
Options: a. 13, b. 17, c. 18, d. 19, e. 12
Example Output:
e