Gold, which has a density of $19\mathrm{.}32$ g$/$cm$3,$ is the most ductile metal and can be pressed into a thin leaf or drawn out into a long fiber. $($a$)$ If a sample of gold with a mass of $2\mathrm{.}386$ g$,$ is pressed into a leaf of $5\mathrm{.}860\backslash$mu m thickness, what is the area of the leaf? $($b$)$ If$,$ instead, the gold is drawn out into a cylindrical fiber of radius $2\mathrm{.}900\backslash$mu m$,$ what is the length of the fiber?