TASK DEFINITION: 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.
PROBLEM: Problem: maxwell leaves his home and walks toward brad ' s house. one hour later, brad leaves his home and runs toward maxwell ' s house. if the distance between their homes is 14 kilometers, maxwell ' s walking speed is 4 km / h, and brad ' s running speed is 6 km / h. what is the total time it takes maxwell before he meets up with brad ?
Options: a. 2, b. 4, c. 5, d. 6, e. 8

SOLUTION: a

PROBLEM: Problem: when positive integer n is divided by 3, the remainder is 1. when n is divided by 7, the remainder is 5. what is the smallest positive integer k such that k + n is a multiple of 21 ?
Options: a. 2, b. 4, c. 6, d. 8, e. 10

SOLUTION: a

PROBLEM: Problem: if the average of 20 digits is 500 and the average of 14 of them is 390, calculate the average of the remaining 6 numbers ?
Options: a. 756.7, b. 751.7, c. 753.7, d. 752.7, e. 722.7

SOLUTION:
a