In order to obtain an industrial steam, after the water vapor in the flue gas formed by burning the lean methane-air mixture is condensed and separated, the oxygen (O2) slots by volume in the remaining gas mixture is 2%. If the air is not preheated, the flue gas temperature is 700 K. a) Calculate to enjoy burning. b) Calculate the thermal cost of the steam boiler with air and methane 298 K. c) When the air is preheated, the exit temperature of the flue gas from the preheater is 433 K. Calculate the thermal gain of the steam boiler if the inlet temperature of the air to the preheater is 298 K and the entry temperature of the methane to the burner is 298 K. d) Calculate the maximum temperature in the combustion area when it is burned at 1 atmosphere pressure by mixing with air according to the methane measure. Note: The chemical formula of methane gas is CH4.