4. A piston-cylinder system initially contains 0.25 kg of ideal gas at Pji=8 bar and ¥1=0.02 m' (State1). After a poly tropic expansion process described by PF = C, the

pressure of gas in the cylinder drops to 2 bar (State 2). During this process, heat transfer between the system and environment occurs.The specific internal energy of the gas decreases by 55 kJ/kg. Ignoring the change in the kinetic energy and potential energy of this system, determine (12 points) (a) the boundary work done by the gas, in kJ (6 points) (b) the heat transfer during the process, in kJ (6 points)