You are pushing a refrigerator across the floor of your kitchen. You exert a horizontal force of 291N for 7.5s, during which time the refrigerator moves a distance of 2.7m at constant velocity. (a) What is the total work (by all forces) done on the refrigerator? (b) What is the work done by friction? How can I calculate the work done by friction if a mass isn't provided and there is no acceleration obviously since there is a constant velocity?