Water pressure vs. area of an object

[ebeck1]

I've been looking at this question for about 1 hour now, and cannot figure out the relationship between the distance an object is at the bottom of the ocean vs. its area... The question is:
A solid copper ball with a diameter of 3.20 m at sea level is placed at the bottom of the ocean, at a depth of 7.0 km. If the density of the seawater is 1030 kg/m3, how much does the diameter of the ball decrease when it reaches bottom?

I used the equation P=Po+pgh to solve for the pressure at the bottom of the ocean but cannot find a relation of initial pressure and initial are to final pressure and final area...

 

[Pyrrhus]

This problem is obviously about volume elasticity, don't they give you the bulk modulus? look for tables in your textbook about bulk modulus of copper and its alloys.