4. Combustion: Methane (CH4) at 25°C, 1 atm enters a furnace operating at steady state and burns completely with 140% theoretical air entering at 400 K, 1 atm. The products of combustion exit at 700 K, 1 atm. Kinetic and potential energy effects are negligible. If the rate of heat transfer from the furnace to the surroundings is 400 kW, determine: a) the balanced reaction equation for the complete combustion of methane with 100% theoretical air; b) the balanced reaction equation for the complete combustion of methane with 140% theoretical air (i.e., 40% excess air); and c) the mass flow rate of methane, in kg/s. Include, with your answer, table(s) summarizing all of the enthalpy values used in your calculations. (25 Marks)