Potential at a Distance away from a FINITE continuously charged plane

[BeRiemann]

Homework Statement

This is primarily a question that I'm trying to program into python. I want to know the potential at some distance (x,y) from the center of a square plane.

Homework Equations

V = integral (k/r) dq

The Attempt at a Solution

The way I see this mathematically is a two integral method. First I figure out the potential from a finite line with a continuous charge. This can be seen as dx or dy, such as the next step integrates this over either the width or length of the plane. If the point had no shift in x, it could be imagined as a pyramid.
I have the line charge done, though it is in terms of lambda = Q/L, when I actually have a sigma = Q/A. With an even charge distribution, I should be able to substitute (Q/(Length*width)) for lambda as long as I use it in both integrals.

Again, just looking for some advice into the method or the setup of the integration. I can take it from there in terms of the programming or simplifying.

 

[BeRiemann]

As a reference I'm trying to do this
http://www.physics.upenn.edu/courses/gladney/phys151/lectures/lecture_jan_17_2003.shtml#tth_sEc1.3.3
but with electric potential in a general form.