Swimming at 0.15 m/s relative to still water, a swimmer heads directly across a 100-m-wide river. He arrives 50 m downstream from a point directly across the river from his starting point. a) What is the speed of the current in the river? b) In what direction should the swimmer head so as to arrive at a point directly opposite his starting point? I got 13.3 meters/second for part (a). Can someone check this? For part (b), I am unsure of what to do. Can someone give me a hint in the right direction?