Four lightweight, plastic spheres, labeled A, B, C, and D, are suspended from threads in various combinations,

Question:

Four lightweight, plastic spheres, labeled A, B, C, and D, are suspended from threads in various combinations, as illustrated in FIGURE 19-47. It is given that the net charge on sphere D is +Q, and that the other spheres have net charges of +Q, - Q, or 0. From the results of the four experiments shown in Figure 19-47, and the fact that the spheres have equal masses, determine the net charge of
(a) Sphere A,
(b) Sphere B,
(c) Sphere C.
Figure 19-47