Answer:
Part a)

Part b)

Explanation:
As we know that electric force on electric charge is given as

here we have

E = 153 N/C
now force is given as

Gravitational force on electric charge near surface of earth is given as


now the ratio of two forces is given as


Part b)
Now the ball is balanced by the electric force and the force of gravity on it
so here we have



here we have

I think 36m/12s because 3×12 =36
Answer: B. I hope you get this right.
The instantaneous velocity of the object is its speed and direction at that instant.