A paint shop compressor has a storage tank for compressed air with a volume of 1 m³. It initially contains air at 1 MPa and 400 k. The feed valve is opened and air flows into the tank until the pressure reaches 5 MPa and the inside temperature is 450K. At that time the valve closes. Determine the amount of air that was introduced into the tank. Finally, after the tank cools down, it reaches a room temperature of 300 K. Determine the air pressure at that condition.