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