3. An old pipe 12 in. in diameter has a roughness of $$e = 0.1 in$$. A $$ \frac{1}{2} $$-in.-thick lining would re-

duce the roughness to $$ε = 0.0004 in$$. How much in pumping cost would be saved per year per 1,000 ft of pipe for water at 70°F with a velocity of 8 ft/s? The pump and motor are 54 per-

cent efficient, and energy costs 8¢/kWh. Would this be economically feasible if it cost $50/ft to reline the pipe?