A bungee jumper has a mass of 50kg and falls straight 40m downward from a bridge. If they are then traveling at -10m/s, the work done by gravity has been ______ and the work done by the bungee cord has been _________.
a. -20,000 N•m, 20,000 N•m
b. -20,000 N•m, 2,500 N•m
c. 2,500 N•m, 0 N•m
d. 20,000 N•m, -17,500 N•m
