Problem $8\mathrm{.}84$

A certain process requires $3\mathrm{.}2$ cfs of water to be delivered at a pressure of $30$ psi $.$ This water comes from a large diameter supply main in which the pressure remains at $60$ psi $.$ The entrance loss coefficient is $0\mathrm{.}5.$ If the galvanized iron pipe connecting the two locations is $200$ ft long and contains six threaded $90$ elbows, determine the pipe diameter. Elevation differences are negligible.