Boats A and B go 240 km downstream and come back to the starting point in 16 hours and 9 hours respectively. If the ratio of the still water speed of Boat A to that of Boat B is 2 : 3, then what is the speed of the stream?
1
5 km/hr
2
10 km/hr
3
15 km/hr
4
20 km/hr
5
25 km/hr