Four identical metallic spheres with charges of +7.0C, +4.2C, 5.0C, and 3.6C are placed on a piece of paper.

Four identical metallic spheres with charges of +7.0µC, +4.2µC, −5.0µC, and −3.6µC are placed on a piece of paper. The paper is lifted on all corners so that the spheres come into contact with each other simultaneously. The paper is then flattened so that the metallic spheres become separated.

(a) What is the resulting charge on each sphere?

(b) How many excess or absent electrons (depending on the sign of your answer to part (a)) correspond to the resulting charge on each sphere?