A train rolls past a stationary observer. To him, the train is moving at a speed
of 25 m/s west, and a woman on the train is moving at a speed of 24.6 m/s
west. How long does it take the woman to move 4 m relative to the train?
A. 7.1 s
B. 9.0 s
C. 8.4 s
D. 10 s