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: how many multiples of 4 are there between 12 and 104, inclusive ?
Options: a. 21, b. 22, c. 23, d. 24, e. 25
Example Output: d

Example Input: Problem: what is the area of a regular hexagon with sides 1 in. long ?
Options: a. 1.59 square inch, b. 2.59 square inch, c. 3.59 square inch, d. 4.59 square inch, e. 2.69 square inch
Example Output: b

Example Input: Problem: what is 3 / 4 of 4 / 5 of 2 / 3 ?
Options: a. 1 / 4, b. 2 / 5, c. 9 / 16, d. 5 / 8, e. 16 / 9
Example Output:
b