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: for the past n days, the average ( arithmetic mean ) daily production at a company was 50 units. if today ' s production of 110 units raises the average to 55 units per day, what is the value of n ?
Options: a. 9, b. 11, c. 13, d. 15, e. 17

Ex Output:
b

Ex Input:
Problem: out of 40 applicants to a law school, 15 majored in political science, 20 had a grade point average higher than 3.0, and 10 did not major in political science and had a gpa equal to or lower than 3.0. how many e applicants majored in political science and had a gpa higher than 3.0 ?
Options: a. 5, b. 10, c. 15, d. 25, e. 35

Ex Output:
a

Ex Input:
Problem: a salesman sold twice as much pears in the afternoon than in the morning. if he sold $ 360 kilograms of pears that day, how many kilograms did he sell in the morning and how many in the afternoon ?
Options: a. 120, b. 180, c. 240, d. 280, e. 320

Ex Output:
c