A 250 kg refrigerator needs to be lifted up to the second floor of a house that is 7 m above the ground level. a. How much work is required to lift the fridge straight up? b. What force is required to do the lifting? c. How does the force and work required change if using a pulley system that divides the weight of the fridge evenly between 4 lengths of rope? d. What length of rope is pulled in order to raise the fridge 7 m? e. Instead of lifting straight up the fridge is pushed up the stairs, which are 21 m long. How much force is required to get the fridge to the top of the stairs along a frictionless ramp?