Sulfur Can Be Separated from Lead in the Mineral Galena $\rarr$

Sulfur can be separated from lead in the mineral galena, PbS(s) , by "roasting" the ore in the presence of oxygen as shown in the following reaction: 2PbS(s) + 3O₂(g) $\rarr$ 2PbO(s) + 2SO₂(g)
Determine $\Delta$ G for the above reaction at 850 ^$\circ$ C. $\begin{array}{|l|c|c|}\hline & \Delta \mathrm{H}_{\mathrm{f}}^{\circ}(\mathrm{kJ} / \mathrm{mol}) & \mathrm{S}^{\circ}(\mathrm{J} / \mathrm{K} \cdot \mathrm{~mol}) \\\hline \mathrm{PbS}(s) & -94.3 & 91.2 \\\hline \mathrm{O}_{2}(g) & 0 & 205.0 \\\hline \mathrm{PbO}(s) & -217.86 & 69.45 \\\hline \mathrm{SO}_{2}(g) & -296.4 & 248.5 \\\hline\end{array}$

A) -620 kJ/mol
B) -640 kJ/mol
C) -660 kJ/mol
D) -680 kJ/mol
E) None of the above