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 student travels from his house to school at 12 km / hr and reaches school 2 hours late. the next day he travels 20 km / hr and reaches school 1 hour early. what is the distance between his house and the school ?
Options: a. 90, b. 100, c. 110, d. 120, e. 130
Example Output: a

Example Input: Problem: if a and b are the roots of the equation x 2 - 9 x + 9 = 0, then the value of a 2 + b 2 is :
Options: a. 63, b. 24, c. 17, d. 6, e. 5
Example Output: a

Example Input: Problem: a person incurs a loss of 5 % be selling a watch for rs. 1140. at what price should the watch be sold to earn 5 % profit.
Options: a. rs. 1200, b. rs. 1230, c. rs. 1260, d. rs. 1290, e. rs. 1270
Example Output:
c