problem 12. Four charged particles are placed so that each particle is at the corner of a square. The sides of the square are 13 cm. The charge at the upper left corner 3.6 uC, the charge at upper right corner -6.5 uC, the charge at lower left corner, and the charge at the lower right corner is -9.1 uC. What is the magnitude of the net electric force on the 3.6 uC charge? Answer in N. Note: What formula(s) should I use?