5. A venturi meter is to be installed in a sch. 40 4 inch line to measure the flow of water. The maximum flow rate is expected to be 325 gal/min at 60 F. the 50 in manometer used to measure the differential pressure is to be filled with mercury, and water is to fill the leads about the mercury surface. The water temperature is to be 60 F throughout. What throat diameter should be specified for the venturi, to the nearest 1/8 inch