A parallel plate capacitor has a charge of 0.020C on each plate with a potential difference of

Question:

A parallel plate capacitor has a charge of 0.020μC on each plate with a potential difference of 240 V. The parallel plates are separated by 0.40 mm of air.
(a) What is the capacitance for this capacitor?
(b) What is the area of a single plate?
(c) At what voltage will the air between the plates become ionized? Assume a dielectric strength of 3.0 kV/mm for air.