A spring is mounted vertically at the bottom of an empty swimming pool. A block of mass M = 857 kg is attached to the spring, and it compresses the spring from its equilibrium position by distance xo. Now the swimming pool is filled with fresh water, and the block is submerged. You find the the spring is now extended distance x = 1.73xo from its equilibrium position. Find the density of the block. I have zero clue how to start...can someone please help?