Calculating Electric Field of a Square Wire

[anap40]

I need to calculate the electric field caused by a square of wire.

I can get the field caused by the sides of the square that are perpendicular to the x-axis but I can't figure out how to get the field caused by the side parrallel to the x axis.

here is an image of the problem.
http://img152.imageshack.us/my.php?image=46151722si8.png

At the origin there is no force in the x direction but in other places there is.

I know the the electric field = (k)q/r^2 but when I try to integrate I think I will need 3 variables.

I'd appreciate any help.

 

[tongpu]

Uh are you sure you are not suppose to find the electric field at a given point? Also maybe placing the square wire in the x-y plane will make it simpler. Regarding needing three variables k is constant, r varies (a function of a variable ex. X), and you take a small element of charge dQ (which should have dx or whatever you choose).