What is the correct balanced equation for the reduction half-reaction that occurs during this roasting process?

Litharg, PbO, is an ore that can be rosated in the presence of carbon monoxide, CO, to produce elemental lead. The reaction that takes place during this roasting process is represented by the balanced equation;

PbO (s) + CO (g) = Pb (l) + CO2 (g)

The correct balanced equation for the reduction half-reaction that occurs during the roasting process is

Pb²⁺ + 2e = Pb