How Do You Calculate the Potential Energy of a Charge in a Square Configuration?

[mattdespat]

1.
Find the potential energy of a charge q= 1mC at the centre of the square made of 4 charged rods of L =20cm and Q=1mC each.

The Attempt at a Solution

I am having quite a bit of trouble with this question, the problem is I don't really know where to start. I feel once i get on the right path I will be able to get it.

 

[CompuChip]

Let's start with this: do you know any formulas involving the potential energy?