Calculate the enthalpy of combustion of methane, ethane, propane, butane and their mixture, which corresponds to the composition of natural gas: methane (96.5%), ethane (1.56%), propane (0.44%), butane (0.15%) ). How much heat will be released during the combustion of 1 m3 of each of the gases and 1 m3 (one cubic meter) of natural gas?