Hello - I worked out this problem but I got a wrong answer. First, I used the Pythagorean theorem to find the radial distance between A and each charges. So 1.2m divided by 2 (= 0.6), then the square root of .6 squared + .6 squared = .849, which is the radius. Then I used Coulomb's Law to calculate the net force: kqAq1/R2 + kqAq2/R2 + ... and so forth. I took out the kqA/R2, which is the same for all, and came up with: kqA/R2 (q1 + q2 + q3 + q4). But it so happens that the numbers inside the parenthesis turns out to be 0. What did I do wrong?