Air from a line at 1800 lbf/in.2, 60 F, flows into a 20-ft3 rigid tank that initially contained air at ambient conditions, 14.7 lbf/in 2, 60F. The process occurs rapidly and is essentially adiabatic. The valve is closed when the pressure inside reaches some value, P2. The tank eventually cools to room temperature, at which time the pressure inside is 750 lbf/in 2. What is the pressure P2? What is the net entropy change for the overall process?