Density, volume and buoyancy, oh my!

1. At Lagoon, there is a large granite rock ball that is supported by water pressure, so people can spin the rock. The diameter of the rock is 1.3m. Granite has a density of 2691kg/m^3. Let’s assume a water pressure if 50 lbs/in^2. Calculate the area of the ball that must be in the water under pressure in order for the ball to “float”.

2. I was given A=2691kg/m^3 * 2.2 lbs/kg * 4/3 x pi * (.65m)^2 * in^2/50lbs = 136.2 in^2 though I am not sure what full relevancy this has to the problem. Is this the answer to the equation or a beneficial equation?

3. I am attempting to help my niece as I am the only one in my family who went beyond pre-algebra in school but this is beyond me. Any help (if possible, I know I am breaking the rules with not having attempts to solve it) would be appreciated.

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