Bowling balls can be made from a variety of substances and are needed to have a circumference of roughly 27.2 inches. The construction of the ball typically consists of a high density core surrounded with a lower density shell. Presume a bowling ball floats in water with half of its volume submerged. If the specific gravity of the shell is 0.350 and the specific gravity of the core is 0.920, compute the thickness of the shell.