a) Southward you need to apply right hand rule. If you close your hand to the east, your thumb will indicate south.
b) Given the equation for Magnetic Force

Replacing


c) Given the second Newton's Law by


Given the electric force by,



Answer:
The average force exerted on the window due to two snowballs is 6 N
Explanation:
Given:
Mass of snowballs
Kg
Velocity of snowball 
For finding the average force,
Force is equal to the change in momentum,

Here, final velocity is zero so we write,

Where
sec

N
Above value of force is due to one ball, but here given in question there are two ball,

N
Therefore, the average force exerted on the window due to two snowballs is 6 N
It has a crystal stucture