It is required to produce 20,000 m per day of potable water having a salt concentration not more than 300 ppm from sea water containing 3.3% salt. An asymmetric cellulose acetate membrane (thickness = 0.8 micron) having a water permeability of 70 I/m.h.MPa and salt rejection of 98% is used. The feed-side pressure is 75 atm, that on the permeate side is 1 atm. If 30% of the feed water permeates through the membrane, estimate the required membrane area. The polarization modulus is 1.2.