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.

[Q]: 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
[A]: c

[Q]: Problem: the total age of a and b is 12 year more than the total age of b and c. c is how many years younger than a ?
Options: a. 12, b. 24, c. data inadequate, d. none of these, e. 34
[A]: a

[Q]: Problem: in a garment industry, 12 men working 8 hours per day complete a piece of work in 10 days. to complete the same work in 8 days, working 15 hours a day, the number of men required is :
Options: a. 4, b. 5, c. 6, d. 8, e. 9
[A]:
d