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: what is the tens digit of 6 ^ 10 ?
Options: a. 7, b. 3, c. 5, d. 1, e. 9
Example Output: a

Example Input: Problem: the probability of two events a and b are 0.25 and 0.40 respectively. the probability that both a and b occur is 0.15. the probability that neither a nor b occur is _________
Options: a. 0.45, b. 0.4, c. 0.5, d. 0.05, e. 0.6
Example Output: c

Example Input: Problem: a small table has a length of 12 inches and a breadth of b inches. cubes are placed on the surface of the table so as to cover the entire surface. the maximum side of such cubes is found to be 4 inches. also, a few such tables are arranged to form a square. the minimum length of side possible for such a square is 48 inches. find b.
Options: a. 8, b. 16, c. 24, d. 32, e. 48
Example Output:
b