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: if julie rows 32 km upstream and 72 km down steam taking 4 hours each, then the speed of the stream
Options: a. 1.5 kmph, b. 0.5 kmph, c. 0.4 kmph, d. 1.6 kmph, e. 2.5 kmph

Ex Output:
b


Ex Input:
Problem: farm tax is levied on the 45 % of the cultivated land. the tax department collected total $ 3840 through the farm tax from the village of mr. willam. mr. willam paid only $ 480 as farm tax. the percentage of total land of mr. willam over the total taxable land of the village is :
Options: a. 15 %, b. 25 %, c. 15.125 %, d. 27.78 %, e. none

Ex Output:
d


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