HW#2/Calculate the time rate of change of air density during expiration. Assume that the lung, has a total volume of 6000 mL, the diameter of the trachea is 18 mm, the air flow velocity out of the trachea is 20 cm/s, and the density of air is 1.225 kg/m3. Also assume that lung volume is decreasing at a rate of 100 mL/s.