In a water pump device, a rope-pulley system is used to connect a diesel engine to the pump transferring 650 kW. The pulley has a diameter of 350 cm and runs at 100 r.p.m. The angle of lap is 150 and the angle of groove is 45. The rope has a mass density of 2 kg/m and can withstand a maximum tension of 2100 N. The coefficient of friction between the ropes and the groove sides is 0.3. Determine the number of ropes required