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,



In physics the standard unit of weight is Newton, and the standard unit of mass is the kilogram. On Earth, a 1 kg object weighs 9.8 N, so to find the weight of an object in N simply multiply the mass by 9.8 N. Or, to find the mass in kg, divide the weight by 9.8 N.
A. The cliff was 30.7 m high
B. I also got 9.5 as the horizontal distance
Here is my work, I find making charts like this one to find knowns and unknowns can be helpful
Potential energy can be found using this formula:
PE= m * g * h
where:
PE= potential energy
m=mass
g=gravitational acceleration constant (9.8 m/s^2)
h= height
So your answer is height because you also use the gravitational constant.