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: if the population of a certain country increases at the rate of one person every 15 seconds, by how many persons does the population increase in 25 minutes ?
Options: a. 80, b. 100, c. 150, d. 240, e. 300
[A]: b


[Q]: Problem: if jack walked 8 miles in 1 hour and 15 minutes, what was his rate of walking in miles per hour ?
Options: a. 4, b. 4.5, c. 6, d. 6.4, e. 15
[A]: d


[Q]: Problem: if a tire rotates at 400 revolutions per minute when the car is traveling 24 km / h, what is the circumference of the tire ?
Options: a. 1 meters, b. 6 meters, c. 5 meters, d. 3 meters, e. 7 meters
[A]:
a