A reverse osmosis plant is to be designed to produce 50 kg/s of boiler feed water with less than 20 ppmw of NaCl starting from sea water that contains 3.5 wt% NaCl. The 40 m² membrane modules operate at 60 atm and achieve a flux of 0.4 m³/m².day when the permeate pressure is 2 atm. If each membrane module has a rejection of 96% of the salt fed to it, determine the overall membrane sequence and the water feed rate required.