A field sample of medium sand with median grain size of 0.84 mm will be tested to determine the hydraulic conductivity using a constant-head permeameter. The sample has the length of 30 cm and a diameter of 5 cm. For pure water at 20 C, estimate the range of piezometric head differences to be used in test. Note: Darcy's law is only valid when Re is less than or equal to 1. Medium sand hydraulic conductivity can be take as K = 12m/day.