Use the _DfH° and _DrH° information Provided to Calculate _DfH°

Use the _DfH° and _DrH° information provided to calculate _DfH° for SO₃(g) : $$\begin{array} { l } \mathrm { D } _ { \mathrm { f } } H ^ { \circ } \left( \mathrm { kJ } \mathrm { mol } ^ { - 1 } \right) \quad 2 \mathrm { SO } _ { 2 } ( g ) + \mathrm { O } _ { 2 } ( g ) \rightarrow 2 \mathrm { SO } _ { 3 } ( g ) \quad \mathrm { D } _ { \mathrm { r } } H ^ { \circ } = - 198 \mathrm {~kJ} \\\mathrm { SO } _ { 2 } ( g ) \quad - 297 \\\end{array}$$

A) -792 kJ mol^-1
B) -248 kJ mol^-1
C) -495 kJ mol^-1
D) -578 kJ mol^-1
E) -396 kJ mol^-1