Consider three identical metal spheres, A, B, and C. Sphere A
carries a charge of +6q. Sphere B carries a charge of -9q. Sphere C
carries no net charge. Spheres A and B are touched together and
then separated. Sphere C is then touched to sphere A and separated
from it. Last, sphere C is touched to sphere B and separated from
it. For the following questions, express your answers in terms of
q. (a) How much charge ends up on sphere C?