A 6-ft-diameter pipeline 4 miles long between two reservoirs of surface elevations 500 and \(300 \mathrm{ft}\) carries a flow rate of \(250 \mathrm{cfs}\) of water \(\left(68^{\circ} \mathrm{F}\right)\). It is proposed to increase the flow rate through the line by installing a glass-smooth liner. Above what liner diameter may an increase of flow rate be expected? What is the maximum increase to be expected? Assume the 6 -ft diameter to be measured to the midpoint of the roughness projections. Neglect all local head losses.