Physics Homework Help?

Chris jumps off a bridge with a bungee cord (a heavy stretchable cord) tied around his ankle, (Figure 1) . He falls for 15 m before the bungee cord begins to stretch. Chris's mass is 78 kg and we assume the cord obeys Hooke's law, F=−kx, with 56 N/m .

If we neglect air resistance, estimate what distance d below the bridge Chris's foot will be before coming to a stop. Ignore the mass of the cord (not realistic, however) and treat Chris as a particle.