Chris spends his spare time running a bungee jumping service off the Henley Street bridge. He has a 123 ft long bungee cord (unstretched) that has a spring stiffness of 34 lb/ft. To test his bungee, he ties the bungee cord to the bridge railing, ties the other end to an unnamed Estabrook professor weighing 130 pounds, and then gently nudges the professor off of the bridge. Assuming he hasn't hit the water, how much has the bungee chord stretched when the professor is at the bottom of the jump? (ft)