The way to solve this, i tried is by saying F = k(q1)(q2) / r^2. So, the force between the two charges is (9x10^9)(2.6x10^-8)(5.5x10^-8) / (1.4^2). Although, from there I'm not sure where to go because that just solves for the force inbetween the two charges and not the EPE or even more specifically the EPE midway between them. I started by saying that Electric Force = k(q1)(q2) / r^2, Then I figured I would apply that to all 3 charges with the +8charge as q2. Next I would add up all the three forces together to find the total amount of force needed. Except, theres where I get stuck, since that single equation can't be applied to all 3 charges seperately since - don't they all effect one charge? Any help appreciated.