Calculate the mass of each of the following: (a) a sphere of gold with a radius of $10.0 \mathrm{cm}$ (volume of a sphere with a radius $r$ is $V=4 / 3 \pi r^{3} ;$ density of gold $=19.3 \mathrm{g} / \mathrm{cm}^{3},$ (b) a cube of platinum of edge length $\left.0.040 \mathrm{mm} \text { (density }=21.4 \mathrm{g} / \mathrm{cm}^{3}\right),(\mathrm{c}) 50.0 \mathrm{mL}$ of
ethanol (density $=0.798 \mathrm{g} / \mathrm{mL}$ ).