An oil pump draws 44 kW of electric power while pumping oil (ρ = 860 kg/m^{3}) at 0.1 m^{3}/s. The pipe diameters are 8 cm at the inlet and 12 cm at the outlet. The pressure rise of the oil across the pump is 500 kPa and the motor efficiency is 90 percent. Determine the mechanical efficiency of the pump (answer in %).