Tom D. spends his spare time running a bungee jumping service off the Henley Street bridge. He has a 153 ft long bungee cord (unstretched) that has a spring stiffness of 22 lb/ft. To test his bungee, he ties the bungee cord to the bridge railing, ties the other end to an unnamed person weighing 135 pounds, and then gently nudges the person off of the bridge. Determine the professor's speed when the bungee cord starts to stretch.