A boat moves through the water of a river at 15 m/s relative to the water, regardless of the boat's direction. If the water in the river is flowing...

A boat moves through the water of a river at 15 m/s relative to the water, regardless of the boat's direction. If the water in the river is flowing at 1.5 m/s, how long does it take the boat to make a round trip consisting of a 220 m displacement downstream followed by a 220 m displacement upstream?