42. Solving a chemistry problem

The heat of combustion of liquid benzene is -3267.7 kJ/mol. The heat of combustion of gaseous acetylene under the same conditions is -1299.6 kJ/mol. Calculate the heats of formation of liquid benzene and gaseous acetylene, as well as the heats of formation of benzene from acetylene under the conditions: 1) P=const ; 2) V=const if the heats of formation of CO2(g) and H2O(l) are respectively -393.5 and -285.8 kJ/mol.