A rigid tank, 0.4 m^3, contains air at 400 kPa and 30*C and is connected by a valve to a piston-cylinder device with zero clearance. The mass of the piston is such that a pressure of 200 kPa is required to raise the piston. The valve is now opened slightly, and air is allowed to flow into the culinder until the tank pressure drops to 200 kPa. During this process heat is transferred to the system to maintain the air within the system at 30*C. Determine this heat transfer (kJ).