Particle A, located at the origin, carries a charge of \(6.0 \mathrm{nC}\).

(a) What is the electrostatic potential (relative to zero potential at infinity) at a position \(r=8.0 \mathrm{~cm}\) from particle A?

(b) With particle A held in place, how much work must be done by an external force to bring particle \(\mathrm{B}\), also carrying a \(6.0-\mathrm{nC}\) charge, from infinity to a distance \(r=8.0 \mathrm{~cm}\) from particle A?

(c) Particle B is returned to infinity, and particle A is moved to \(r=8.0 \mathrm{~cm}\) and held there. How much work must be done by an outside agent to bring particle B from infinity to the origin?