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: 40 is subtracted from 60 % of a number, the result is 50. find the number ?
Options: a. 150, b. 330, c. 277, d. 279, e. 712

Ex Output:
a

Ex Input:
Problem: a bag of potatoes weighs 60 lbs divided by half of its weight. how much does the bag of potatoes weight ?
Options: a. 20 lb, b. 11 lb, c. 10 lb, d. 15 lb, e. 5 lb

Ex Output:
b

Ex Input:
Problem: the grade point average of the entire class is 90. if the average of one third of the class is 96, what is the average of the rest ?
Options: a. 92, b. 89, c. 88, d. 87, e. 86

Ex Output:
d