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: excluding the stoppages, the speed of a bus is 48 km / hr and including the stoppages the speed of the bus is 12 km / hr. for how many minutes does the bus stop per hour ?
Options: a. 45 min, b. 10 min, c. 12 min, d. 20 min, e. 18 min

Ex Output:
a


Ex Input:
Problem: in a room filled with 6 people, all 6 people have exactly 1 sibling in the room. if two individuals are selected from the room at random, what is the probability that those two individuals are not siblings ?
Options: a. 3 / 5, b. 4 / 5, c. 5 / 6, d. 5 / 12, e. 7 / 12

Ex Output:
b


Ex Input:
Problem: a 50 ml after - shave lotion at 30 % alcohol is mixed with 30 ml of pure water. what is the percentage of alcohol in the new solution ?
Options: a. 16.75 %, b. 17.75 %, c. 18.75 %, d. 19.75 %, e. none of these

Ex Output:

c