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 dimensions of a room are 10 m x 7 m x 5 m. there are 2 doors and 3 windows in the room. the dimensions of the doors are 1 m x 3 m. one window is of size 2 m x 1.5 m and the other 2 windows are of size 1 m x 1.5 m. the cost of painting the walls at rs. 3 per sq m is
Options: a. 2488, b. 378, c. 739, d. 474, e. 291
Example Output: d

Example Input: Problem: the speed of a boat in still water is 15 km / hr and the rate of current is 3 km / hr. the distance travelled downstream in 24 minutes is
Options: a. 17.2 km, b. 7.2 km, c. 7.6 km, d. 17.6 km, e. 27.2 km
Example Output: b

Example Input: Problem: if x is the median of the set { 8 / 2, 11 / 3, 27 / 9, 21 / 5, x }, x could be
Options: a. 4, b. 17 / 5, c. 16 / 5, d. 30 / 7, e. 31 / 7
Example Output:
a