NEED CORRECT AND DETAILED SOLUTION!!!!

A pitot tube with a U-tube water manometer is attached to a horizontal oil pipe of 4 in. inside diameter. If the manometer reading is 15 in., determine the volumetric flow rate, in gpm, of oil in the pipe. The pitot opening is placed at the center of the pipe. The oil has a specific gravity of 0.84 and a viscosity of 0.0336 lb/ft-sec. c. 32 b. 55 d. 94 a. 77