Two parallel plates have equal and opposite charges when

Question

Solve the all parts of following question:

Question: Two parallel plates have equal and opposite charges. When the space between the plates is evacuated, the electric field is E= 3.20×10⁵V/m. When the space is filled with dielectric, the electric field is E= 2.00×10⁵V/m.

Part A: What is the charge density on each surface of the dielectric?

Part B: What is the dielectric constant?

I need help to determine the charge density on each surface of the dielectric.