You are asked to help set up a historical display in the park by stacking some cannonballs next to a Revolutionary War cannon. You are told to stack them by starting with a triangle in which each side is composed of four touching cannonballs. You are to continue stacking them until you have a single ball on the top centered over the middle of the triangular base.
a. How many cannonballs do you need?
b. What type of closest packing arrangement is displayed by the cannonballs?
c. The four corners of the pyramid of cannonballs form the corners of what type of regular geometric solid?