Calculating Energy for Creating an Equilateral Triangle of Charges

[azolotor]

How much energy is necessary to place three charges, each of 2.0 μC, at the corners of an equilateral triangle of side 2.0 cm?

This is in the chapter all about electric potential so I think I have to use the voltage equations in some way.

V = Kq/r u= qV



I am honestly unsure of where to start. It seems like it would be the sum of the voltages multiplied by the charges but I don't know if they interact in some way or what the distance r would be.

 

[Saitama]

When you place the first charge, you don't need to do any work but when the second charge is placed, you have to do work because of the electric field present there due to the first charge you placed.