3. A particular fluorinated lubricating oil has a vapor pressure of 2 x 10-6 torr at 386 K. Suppose a steel tube of length 10 cm and inside diameter 5 mm is coated with a uniform layer of this oil, with an initial film thickness of 1 um. How long is required for 90% of the oil to evaporate into an airstream at 386 K, at flow rates in the range of 10 to 1000 cm3/s? The molecular weight of the oil is 8250. The diffusion coefficient of the oil vapor in air is 0.04 cm2/s. The density of the oil is 1900 kg/m3