In a differential wheel and axle, the diameter of wheel is 15 cm and that of axles are 10 and 6 cm..

In a differential wheel and axle, the diameter of wheel is 15 cm and that of axles are 10 and 6 cm. If the efficiency of the machine is 60%, find the effort required to lift a load of 500 N. Calculate the number of revolutions made by machine in lifting the load by a distance of 20 cm.