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

Frequency of a sound wave is commonly referred to as pitch. That is the specialized name for frequency of a sound wave.
Just remember it as pitch.
Surface air pressure is a consequence of the weight of the air acting on its surface. For example, if you are standing on Mars, the pressure around you is what you call the surface air pressure. Thus, that surface air pressure must be 0.007 atm.