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: a certain roller coaster has 6 cars, and a passenger is equally likely to ride in any 1 of the 6 cars each time that passenger rides the roller coaster. if a certain passenger is to ride the roller coaster 6 times, what is the probability that the passenger will ride in each of the 6 cars ?
Options: a. 3 / 1944, b. 1 / 96, c. 2 / 96, d. 1 / 1944, e. 1
Example Output: a

Example Input: Problem: a student travels from his house to school at 10 km / hr and reaches school 2 hours late. the next day he travels 18 km / hr and reaches school 1 hour early. what is the distance between his house and the school ?
Options: a. 65.0, b. 67.5, c. 70.0, d. 72.5, e. 75.0
Example Output: b

Example Input: Problem: by selling 20 pencils for a rupee a man loses 30 %. how many for a rupee should he sell in order to gain 30 % ?
Options: a. 8.56, b. 10.75, c. 14.5, d. 16.5, e. 11.4
Example Output:
b