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: john left home and drove at the rate of 45 mph for 2 hours. he stopped for lunch then drove for another 3 hours at the rate of 45 mph to reach his destination. how many miles did john drive ?
Options: a. 235 miles., b. 245 miles., c. 225 miles., d. 265 miles., e. 275 miles.
Example Output: c

Example 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
Example Output: a

Example Input: Problem: cereal a is 11 % sugar by weight, whereas healthier but less delicious cereal b is 2 % sugar by weight. to make a delicious and healthy mixture that is 5 % sugar, what should be the ratio of cereal a to cereal b, by weight ?
Options: a. 1: 2, b. 2: 3, c. 1: 3, d. 1: 4, e. 3: 4
Example Output:
a