Compute all parts of given question:
Question: A river flows due south with a speed of 2.10m/s . A man steers a motorboat across the river; his velocity relative to the water is 4.00m/s. The river is 850m 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?
Part III: How much time is required to cross the river?
Please show all work and steps to determine the velocity of the boat relative to the earth.