1. The problem statement, all variables and given/known data Four point particles with charges .6 microC, 2.2 microC, -3.6microC, and 4.8 microC are placed at the corners of a square of side 10cm. what is the external work needed to bring a charge of -5 microC from infinity to the center of the square? (Assume the speed of the -5 microC charge is kept constant) 2. Relevant equations V=kq/r(from infinity) w = Q * v Vtotal = V1 + v2...Vn 3. The attempt at a solution 9x10^9 * (-5 x 10^-12) / squareroot(.1^2 + .1^2) * (.6 + 2.2 - 3.6 + 4.8) = -1.28 J answer in book: -2.55J my answer is nearly a perfect factor of 2 away. What's going on here?