2) A person uses a rope and pulley to lift a 75.0 kg sack 2.0 m onto a truck. The downward force on the rope over the 2.0 m distance is 2.5 x 103 N. a) Calculate the work done in raising the sack. (2 marks) b) How much useful work was done (work required to lift the sack)? (2 marks) c) What is the efficiency of the rope and pulley in raising the sack onto the truck? (2 marks)