A tank of 0 05 m3 volume contains air at 800 kPa (absolute) and 15 C. At t =0, air begins escaping from the tank through a valve with a flow area of 65 mm2. The air passing through the valve has a speed of 300 m s and a density of 6 kg m3. Determine the instantaneous rate of change of density in the tank at t =0.