A frictionless piston-cylinder device fitted with stops above the piston contains 1.2 kg of air at 200°C and 700 kPa. This pressure is sufficient to ensure that the piston is pressing up against the stops. A valve at the bottom of the cylinder is now opened, and air escapes from the cylinder. Just as the air pressure reaches exactly 600 kPa, the piston is observed to begin to move downwards. The valve is closed when the cylinder volume has declined to 80% of its initial volume. During the air loss process, 40 kJ of heat is lost from the cylinder. Determine (i) the final temperature of the air in the cylinder, (ii) the work done, (iii) the mass of air that has escaped from the cylinder, and (iv) answer the question that's given at the end of the following hint. Use ‘best guess' constant specific heat values at the average temperature.