Consider a Carnot engine using air as the working substance. At the beginning of the isothermal expansion, the air is at 550 kPa and occupies a volume of 5 liters. The pressure and volume at the end of the adiabatic expansion are 150 kPa and 15 liters. Determine the efficiency of the engine. 2. A Carnot refrigerator removes 16 000 kJ/min from a cold storage room at - 20C. Heat is discharged to the atmosphere at 20C. Determine the power required.