A glycerin pump is powered by a 5-kW electric motor. The pressure differential between the outlet and the inlet of the pump at full load is measured to be 211 kPa. If the flow ratethrough the pump is 18 L/s and the changes in elevation and the flow velocity across the pump are negligible, the overall efficiency of the pump is
(a) 69 percent
(b) 72 percent
(c) 76 percent
(d) 79 percent
(e) 82 percent