Log1989 problem № 13.9

Two metal plates charged with charges q₁=5.4 nC and q₂=1.7 nC are located parallel to each other at a distance of d=1.5 mm. The area of ​​each plate is S=1900 cm². Considering that the linear dimensions of the plates are incommensurably large compared to the distance between the plates and the thickness of the plates, find: a) the surface charge densities on the plates σ₁; σ₂; σ₃; σ₄; b) the potential difference U between the plates.