Answer:
Step-by-step explanation:
Force on a moving charge is given by the following relation
F = q ( v x B )
for proton 
q = e , v = vi , B = Bk 
F = e ( vi x Bk )
= Bev - j 
= - Bevj 
The direction of force is along negative of y axis or -y - axis. 
for electron 
q = - e , v = vi , B = Bk 
F = - e ( vi x Bk )
= - Bev - j 
= Bevj 
The direction of force is along positive of y axis or + y - axis.