A 2.1-m3 rigid tank initially contains air at 100 kPa and 22°C. The tank is connected to a supply line through a valve. Air is flowing in the supply line at 600 kPa and 22°C. The valve is opened, and air is allowed to enter the tank until the pressure in the tank reaches the line pressure, at which point the valve is closed. A thermometer placed in the tank indicates that the air temperature at the final state is 77°C. The gas constant of air is 0.287 kPa·m3/kg·K. The properties of air are hi = 295.17 kJ/kg, u1 = 210.49 kJ/kg, and u2 = 250.02 kJ/kg.

Determine the mass of air that has entered the tank.