A child at a park finds a ball floating in a freshwater pond (temperature 30 degree C). The child swims to the ball and, with an incredible amount of dexterity, balances himself on the ball. When he does so the ball sinks to the point where none of it extends out of the water and remains submerged such that the child does not sink. The child has a mass of 36 kg. What is the diameter of the ball? Assume for this problem that the ball has negligible mass (including the air inside it).