12. A 6-kg object falling from rest from a height of 300 meters acquires a speed 70 m/s just before striking?

12. A 6-kg object falling from rest from a height of 300 meters acquires a speed 70 m/s just before striking the ground. What is the magnitude of the work done (in joules) on the object by air resistance? (a) 3260 (b) 2940 (c) 4120 (d) 6040 (e) None of these