Regarding the Napkin Ring part of the problem. Had the author simplified the formula for "Vanswer" rather than plugging in values for h & c, he would have gott

Regarding the Napkin Ring part of the problem. Had the author simplified the formula for "Vanswer" rather than plugging in values for h & c, he would have gotten: Vanswer = (Pi/6) * h^3 From which is it easy to see that the answer in this particular case is 36 * Pi but it also makes clear that the answer does not depend on R.