Water at 20°C flows in a long horizontal commercial-steel 6-cm-diameter pipe which contains a classical Herschel venturi with a 4-cm throat, the venturi is connected to a mercury manometer whose reading is h = 40 cm. Estimate (a) the flow rate, in m3/h, and (b) the total pressure difference between points 50 cm upstream and 50 cm downstream of the venturi.