A reverse osmosis unit for purifying brackish water has about 900,000 hollow fibers that permit the diffusion of water but rejects most of salt.

A reverse osmosis unit for purifying brackish water has about 900,000 hollow fibers that permit the diffusion of water but rejects most of salt. The fibers are 85 micrometers in outside diameter, 42 micrometers in inside diameter and about 3ft long. The average flow through the tubes is 2000 gal of water every 24 hours. What is the pressure drop within an individual fiber from the feed end to the discharge end?