Here are two examples of floating objects: $($a$)$ A block of wood long by wide by high has a density of and floats in water $($whose density is $).$ How far below the surface of the water is the bottom of the block? Explain your reasoning. $($b$)$ An advertising blimp consists of a gas bag, the supporting structure for the gas bag, and the gondola hung from the bottom, with its cabin, engines, and propellers. The gas bag is about long with a diameter of about $,$ and it is filled with helium $($density about per $22\mathrm{.}4$ l under these conditions$).$ Estimate the total mass of the blimp, including the helium.