Gold $($Au$)$ forms a substitutional solid solution with silver $($Ag$).$ Compute the weight

percent of gold that must be added to silver to yield an alloy that contains $5\mathrm{.}5{10}^{21}$

Au atoms per cubic centimeter. The densities of pure Au and Ag are $19\mathrm{.}32$ and

$10\mathrm{.}49\frac{g}{c}{m}^3,$ respectively.