April swims at v = 1.25 m/s in still water. Starting on the west bank of a south-flowing 50m-wide river, she swims directly east across the river, then immediately turns around and returns to the west bank of the river. Upon reaching this shore, she finds that she is 60 m downstream (south) from her starting point.
(a) What is the speed of the river's current?
(b) If, on first swimming to the east bank, she had wanted to swim straight across the river, ending up directly across the river from her starting point, at what angle (with respect to the east) should have been her heading?