A parallel-plate capacitor has an area of 5.00 cm2, and the plates are separated by 1.00 mm

Question:

A parallel-plate capacitor has an area of 5.00 cm2, and the plates are separated by 1.00 mm with air between them. The capacitor stores a charge of 400 pC.
(a) What is the potential difference across the plates of the capacitor?
(b) What is the magnitude of the uniform electric field in the region between the plates?