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: the area of a square field is 625 km 2. how long will it take for a horse to run around at the speed of 25 km / h ?
Options: a. 12 h, b. 10 h, c. 8 h, d. 4 h, e. none of these
Example Output: d

Example Input: Problem: sandy walked 20 meters towards south. then sandy turned to her left and walked 20 meters. she then turned to her left and walked 20 meters. she then turned to her right and walked 25 meters. what distance is she from the starting point and in which direction ?
Options: a. 35 m east, b. 35 m north, c. 30 m west, d. 45 m west, e. 45 m east
Example Output: e

Example Input: Problem: the ratio between b and y is 7 / 9; b and y are increased by 4, what is the ratio between the new values of b and y ?
Options: a. 7 / 9, b. 14 / 9, c. 7 / 18, d. 11 / 13, e. it can not be determined
Example Output:
e