Electromagnetism: Force between two charged plates

[oondi]

Homework Statement

Coulomb's Law: finding electric force between two metal plates.

Relevant Equations

F=q1*q2/(r^2) (unit position vector)

Hello, I need to find the force between the two metal plates, one is charged positively, and another is charged negatively.
I have to use surface integration, but then I get two surface integrations because of the two differently charged plates.
Now I am confused. Please help me.
Thank you in advance

 

[haruspex]

Homework Statement:: Coulomb's Law: finding electric force between two metal plates.
Relevant Equations:: F=q1*q2/(r^2) (unit position vector)

I have to use surface integration, but then I get two surface integrations because of the two differently charged plates.

Do you mean you get a double integral?
The difficulty, surely, is that the distance between the area elements varies.
Being metal plates, the charge distribution will not be quite uniform, but I would treat it as such.
What is the usual approximation of the field near a large charged plate?