A microfiltration unit used to concentrate a suspension of 0.8-m spherical particles has a permeate flux of

A microfiltration unit used to concentrate a suspension of 0.8-µm spherical particles has a permeate flux of 150 L/m²·h at 30°C and a pressure drop of 2.1 atm. Under the same conditions, the pure water flux was 280 L/m² ·h. How thick a layer of particles would be needed to account for the gel-layer resistance if ε = 0.40?