Question 11
Brad and Jake travel 9 km from A to B. Jake first cycles at $8\text{ km/h}$, leaves the bicycle at some point, then walks at $5\text{ km/h}$ to B. Brad first walks at $4\text{ km/h}$, picks up Jake’s bicycle, then cycles at $10\text{ km/h}$ to B. They start together and arrive at B together. For how many minutes is the bicycle left waiting before Brad uses it?