Four charged particles are arranged in a square as shown in the figure. the length of each of the sides of the square are 6.9 mm and q-+3.9 × 10-6 c. what is the vector sum of the forces exerted on particle d by the other three particles? draw and label the forces acting on d. choose a coordinate system. define all the distances. (hint: center your coordinate system at d. tilt the axis so the net force will be along the x-axis.) q (+ i a