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.

Ex Input:
Problem: kathleen can paint a room in 4 hours, and anthony can paint an identical room in 5 hours. how many hours would it take kathleen and anthony to paint both rooms if they work together at their respective rates ?
Options: a. 8 / 15, b. 40 / 9, c. 15 / 8, d. 9 / 4, e. 15 / 4

Ex Output:
b


Ex Input:
Problem: a man sitting in a train which is traveling at 36 kmph observes that a goods train, traveling in opposite direction, takes 10 seconds to pass him. if the goods train is 240 m long, find its speed
Options: a. 50 kmph, b. 56 kmph, c. 58 kmph, d. 62 kmph, e. 72 kmph

Ex Output:
a


Ex Input:
Problem: a cube of edge 16 cm is immersed completely in a rectangular vessel containing water. if the dimensions of the base of vessel are 20 cm * 15 cm, find the rise in water level ?
Options: a. 6 cm, b. 8.25 cm, c. 13.65 cm, d. 15.12 cm, e. 20.62 cm

Ex Output:

c