Determine the heat of reaction in a welder-s acetylene torch

Question

Given the following equations and Ho values, determine the heat of reaction at 298 K for the reaction which occurs in a welder's acetylene torch:

2 C2H2(g) + 5 O2(g) --> 4 CO2(g) + 2 H2O(l)

H2(g) + 1/2 O2(g) --> H2O(l) Ho/kJ = -285.8
2 C(s) + H2(g) --> C2H2(g) Ho/kJ = +226.7
C(s) + O2(g) --> CO2(g) Ho/kJ = -393.5