请教一道数学题

Silan

A hiker walking at a constant rate of 4 miles per hour is passed by a cyclist traveling in the same direction along the same path at a constant rate of 20 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?



(A)

(B) 15

(C) 20

(D) 25

(E)

答案是C  
prep里的    感觉缺条件~~愣是没做出来！
谢谢了~~~

Silan

呃~ 自己顶下·