Electric Potential Proton Problem

[milkyway200]

Hello there! I'm new to the forums. It seems like a lot of very knowledgeable people are here. I have my first question.

How can the question below be solved?

Thank you for your help.How much work is needed to assemble an atomic nucleus containing three protons (such as Be) if we model it as an equilateral triangle of side 2.00 x 10^-15 m with a proton at each vertex? Assume the protons started from very far away.

 

[Defennder]

0 work is done in placing the first charge. For the second charge, it's just the electric potential due to the first one. Finally the amount of work done for the placement of the last charge is the summation of electric potentials of the first 2 charges. Just sum all of it up.