The deep-submersible research vessel has a passenger compartment in the form of a spherica...

The deep-submersible research vessel has a passenger compartment in the form of a spherical steel shell with a mean radius of 1 m and a thickness of 35 mm. Calculate the mass of lead ballast which the vessel must carry so that the combined weight of the steel shell and lead ballast exactly cancels the combined buoyancy of these two parts alone.