A liquid (viscosity = 0.0016 N-s/m$^2$; density = 1000 kg/m$^3$) is forced through the circular tube shown in the figure below. A differential manometer is connected to the tube as shown to measure the pressure drop along the tube. When the differential reading, $\Delta$h, is 9 mm, what is the mean velocity in the tube?
2.6m
4 mm
Density of gage fluid = 2000 kg/m$^3$
V = 0.027590 m/s