A hollow-fiber dialysis unit is one design that provides a large surface area between blood and dialysate to permit efficient mass exchange.Total blood flow rates in the device are typically 200 mL min^-1, similar to the flow rate in kidneys. A typical hollow-fiber unit is 30 cm long with 250 fibers, each of diameter 200 micrometers. The fluid density is 1.05 g cm^3 and the viscosity is 0.03 g cm^-1s^-1. Assuming that blood behaves as a Newtonian fluid, determine the entrance length for each fiber and assess whether it is small relative to the length of the hollow-fiber unit.