Mort, Who Is Standing on the Ground, Throws a Ball

Multiple Choice

Mort, who is standing on the ground, throws a ball at 20 m/s eastward as measured by him. What is the ball's velocity relative to Velma, who is in a train moving eastward past Mort at 70 m/s?

A) 70 m/s westward
B) 90 m/s westward
C) 50 m/s eastward
D) 50 m/s westward
E) 90 m/s eastward