Calculate standard internal energy change($ \Delta E^{\circ}$) for the reaction \[\] $OF2(g) + H_2O(g) \rightarrow O_2(g) + 2HF(g)$ \[\] Given standard enthalpies of formation $ \Delta H_f^{\circ}\: of\: OF_2(g), H_2O(g)\: and\: HF(g)$ are23, -241.8 and -268.6 kJ/mol respectively.