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: four bells commence tolling together and toll at intervals of 2, 4, 6, 8 seconds respectively. in 18 minutes, how many times do they toll together ?
Options: a. 43, b. 44, c. 45, d. 46, e. 47

Ex Output:
c


Ex Input:
Problem: two trains travel in opposite directions at 36 kmph and 45 kmph and a man sitting in slower train passes the faster train in 8 seconds. the length of the faster train is
Options: a. 80 m, b. 100 m, c. 120 m, d. 180 m, e. 160 m

Ex Output:
b


Ex Input:
Problem: a glass was filled with 10 ounces of water, and 0.03 ounce of the water evaporated each day during a 20 - day period. what percent of the original amount of water evaporated during this period ?
Options: a. 0.006 %, b. 0.06 %, c. 0.6 %, d. 6 %, e. 60 %

Ex Output:

d