Consider these equations:

2S (s) + 3O2 (g)→2SO3 (g), ΔH = −792 kJ
2S (s) + 2O2 (g)→2SO2 (g), ΔH = −594 kJ
2SO2 (g) + O2 (g)→2SO3 (g), ΔH =?

What is the missing ΔH?

a) −294 kJ
b) −198 kJ
c) +198 kJ
d) +294 kJ