At a construction site, I there are two pully systems used to rise concrete to upper level on the building under construction. The first pulley system has 5 pulleys and the second pulley system has 4 pulleys. If four workers are required to rise 250kg of concrete to the upper most level which is 8 meters from the ground in 35 seconds but don't know which pulley system will be efficient. Help the workers which pulley system they should use providing them with the velocity with which the concrete moves up and the power they dissipated.