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: 108 ã — 108 + 92 ã — 92 = ?
Options: a. 20120, b. 11500, c. 20128, d. 20660, e. 20228
Example Output: c

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 particular library has 75 books in a special collection, all of which were in the library at the beginning of the month. these book are occasionally loaned out through an inter - library program. if, by the end of the month, 80 percent of books that were loaned out are returned and there are 67 books in the special collection at that time, how many books of the special collection were loaned out during that month ?
Options: a. 20, b. 30, c. 35, d. 40, e. 55
Example Output:
d