A dense rubber buoy is attached to a lead weight when it is accidentally lost overboard from an ocean going vessel. The density of the buoy at the surface was 661 kg/m^3. What is the density of the buoy when it reaches the ocean floor 6.4 km below given that the bulk modulus of the rubber is a constant 1.8 GN/m^2
[?(water) = 1,000 kg/m^3, g=9.81 m/s^2, P(atmosphere)=10^5N/m^2]