We have a downward laminar flow of oil in a vertically oriented tube. There is no pressure drop along the direction of the flow, so the only driving force for this flow is gravity. Oil viscosity is 0.002 Pa s. Diameter of the tube is 2 mm. Gravitational acceleration is 9.8 m s^-2. What is the density (kg m^-3) of this oil? The downward mass rate was 1 kg/s.