$8\mathrm{.}101$ A certain process requires $2\mathrm{.}3$ 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 $.$ If the galvanized iron pipe connecting the two locations is $200$ ft long and contains six threaded $\backslash (90^\{\backslash$circ$\}\backslash )$ elbows, determine the pipe diameter. Elevation differences are negligible.