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: i flew my tiny seaplane to visit my mother. on the flight up, i flew at 96 mph. on the way home, i flew 88 mph. what was my average speed for the trip ?
Options: a. 198 mph, b. 110 mph, c. 92 mph, d. 100 mph, e. 99 mph
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

Example Input: Problem: one type of liquid contains 10 % of water and the second type of liquid contains 15 % of water. a glass is filled with 5 parts of 1 st liquid and 2 parts of 2 nd liquid. the percentage of water in the new mixture in the glass is ?
Options: a. 5.6 %, b. 11.4 %, c. 15.6 %, d. 21.3 %, e. 18.9 %
Example Output:
b