A V-belt drive is used to connect two shafts 1 m apart for transmitting 75 kW at 1200 rpm of a driver pulley. Take effective diameter of driver pulley = 300 mm, effective diameter of driven pulley = 900 mm, coefficient of friction = 0.25, density of the belt material 1100 kg/m3, the angle of groove = 40, area of the belt section is 400 mm2 and the permissible stress is 2.46 MPa. Calculate the number of belts required and the length of the belt.