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.

Input: Consider Input: Problem: a van takes 5 hours to cover a distance of 495 km. what speed in kph should the van maintain to cover the same distance in 3 / 2 of the previous time ?
Options: a. 60, b. 63, c. 66, d. 69, e. 72

Output: c


Input: Consider Input: Problem: mary works in a restaurant a maximum of 70 hours. for the first 20 hours, she is paid $ 8 per hour. for each overtime hour, she is paid at a rate which is 25 % higher than her regular rate. how much mary can earn in a week ?
Options: a. 600, b. 620, c. 660, d. 320, e. 400

Output: c


Input: Consider Input: Problem: calculate the sum of first 60 natural numbers.
Options: a. 1839, b. 2830, c. 1830, d. 1831, e. 1835


Output: c