You are on a boat that takes its passengers 14 km up the stream. The passengers then disembark and float on tubes 8.0 km down the stream, where they exit the river. The tubes move only with the river current. The total travel time for the passengers (on the boat and on the tubes, combined) is 3.0 hours. The boat's speed in still water is 15 km per hour. What is the speed of the river current with respect to the river banks? Select ALL that apply.