A motorcycle has a velocity of 15 m/s, due south as it passes a car with a velocity of 24 m/s, due north. What is the magnitude and direction of the velocity of the motorcycle as seen by the driver of the car?
a. 9 m/s, north
b. 9 m/s, south
c. 15 m/s, north
d. 39 m/s, north
e. 39 m/s, south