the hiker walking at a constant rate of 7 miles per hour is passed by a cyclist traveling in the same direction along the same path at 28 miles per hour. the cyclist stops to wait for the hiker 5 minutes after passing her, while the hiker continues to walk at her constant rate, how many minutes must the cyclist wait until the hiker catches up?
Answers
A) 10 B) 15 C) 20 D) 25 E) 30

Rationale: "for the 5 minutes the cyclist continues to overtake the hiker , she is going at 21 miles per hour faster than the hiker . once the cyclist stops , the hiker is going at 7 miles per hour while the cyclist is at rest so the amount of time the hiker will take to cover the distance between them is going to be in the ratio of the relative speeds . 21 / 7 * 5 or 15 minutes answer is ( b )"
Answer: B