Your friend rides a bicycle along the edge of a river, starting at point A and riding east at a constant speed of vbike. At the exact same moment, you start swimming from point B on the opposite bank of the river. If you can swim at a speed of vswim relative to the water, and if the river has width W and flows to the easy at a speed of vriver:
a) At what angle must you swim (measured from the eastward bank) in order to reach the opposite bank at the exact time that your friend reaches the same spot?
b) How far downriver from point A will this occur?