An ultrafiltration process is being used to concentrate an orange solution. The retentate volume after 4 h of operation is 0.5 m³ and the retentate is five times more concentrated than the feed. The enzyme does not leak through the membrane. If the initial orange concentration in the feed was 34 kg m^-3, the initial permeate flux was 0.045 m³ m^-2 h^-1 and the final flux was 0.006 m³ m^-2 h^-1, determine the following:

(i) the mass transfer coefficient (k) at the membrane;

(ii) the protein concentration (c_m) at the surface of the membrane.