Calculate ∆Hrxn for

Ca(s) + 1⁄2 O2(g) + Co2 (g) → CaCO3(s) given the following set of reactions:

Ca(s) + 1⁄2 O2(g) →CaO(s) ∆H = -635.1 kJ CaCO3(s) →CaO(s) + CO2(g) ∆H = 178.3 kJ