6) A piston-cylinder device contains 0.2kg of air initially at 2.3MPa and 380C. The air is first expanded isothermally to 550kPa, then compressed polytropically with a polytropic exponent of 1.2 to the initial pressure, and finally compressed at the constant pressure to the initial state. Determine a) The boundary work for each process. 12P b) The net work of the cycle. 4P