Need Chemistry Help with standard enthalpy

Given the standard enthalpy changes for the following two reactions:
(1)2Hg(l) + O2(g)2HgO(s)…… ΔH° = -181.6 kJ
(2)Hg(l) + Cl2(g)HgCl2(s)……ΔH° = -224.3 kJ
what is the standard enthalpy change for the reaction:
(3)2HgCl2(s) + O2(g)2HgO(s) + 2Cl2(g) ΔH° = ?