Answer variants:
6 km/hr
7.5 km/hr
4 km/hr
3 km/hr
The speed of a boat in still water is 9 \(km/hr\). It can move 15 \(km\) upstream and 26 \(km\) downstream in 5 hours. Determine the speed of the stream.
 
The speed of the stream \(=\)
.