Combustion air supplied to the furnace burners is preheated with exhaust gas from a furnace in a cross-flow heat exchanger. The exhaust gas has a mass flow rate of 15 kg/s and an inlet temperature of 827 °C. The air has a mass flow rate of 10 kg/s and ambient temperature of 27 °C, and it flows perpendicular to the tubes. The tubes are unfinned, and the overall heat transfer coefficient is 100 W/m2 · K. Determine the total tube surface area required to achieve an air outlet temperature of 577 °C. Take both the exhaust gas and the combustion air to have the same properties of those of ideal air. Do not iterate.