Proton a Travels Northward with a Constant Velocity

Multiple Choice

Proton A travels northward with a constant velocity.Due north of proton A is proton B,traveling to the east at a different constant velocity.In what direction is the magnetic force on B?

A) to the south
B) to the west
C) upward,out of the ground
D) down into the ground
E) There is no force on B.