The refrigerant R-152a, difluoroethane, is tested by the following procedure. A 10-L evacuated tank is connected to a line flowing saturated-vapor R-152a at 40C. The valve is then opened, and the fluid flows in rapidly, so that the process is essentially adiabatic. The valve is to be closed when the pressure reaches a certain value P2, and the tank will then be disconnected from the line. After a period of time, the temperature inside the tank will return to ambient temperature, 25C, through heat transfer with the surroundings. At this time, the pressure inside the tank must be 500 kPa. What is the pressure P2 at which the valve should be closed during the filling process? The ideal gas specific heat of R-152a is CP0 = 0.996 kJ/kg K.