A Man at Point a Directs His Rowboat Due North

Multiple Choice

A man at point A directs his rowboat due north toward point B, straight across a river of width 100 m. The river current is due east. The man starts across, rowing steadily at 0.75 m/s and reaches the other side of the river at point C, 150 m downstream from his starting point.
-What is the speed of the river?

A) 0.38 m/s
B) 0.67 m/s
C) 1.1 m/s
D) 6.7 m/s
E) 7.5 m/s