Solve the all parts of following problem:

Problem: A river flows due south with a speed of 2.30m/s. A man steers a motorboat across the river; his velocity relative to the water is 4.00m/s. The river is 800m wide.

Part I: In which direction should the motorboat head in order to reach a point on the opposite bank directly east from the starting point? (The boat's speed relative to the water remains 4.00m/s).

Part II: What is the velocity of the boat relative to the earth?

_________ m/s

Part III: How much time is required to cross the river?

t= ______ s

I don't just need an answer, work and explanations/walkthrough would be much appreciated! Thanks.