(4) A passenger plane is flying at an altitude of 40,000 feet. Outside air temperature is -55 C and the pressure is 0.2 bar. Fresh air will need to be compressed to 1 bar and heated to 25C before being introduced into the cabin. The plane's cabin has a volume of 120 m. Calculate the cost of refreshing the cabin air every 1 minute if energy costs 0.78 per kW hr. The air is assumed to be an ideal gas with Cp = 30 (J/molK). [10] =