Earth's surface area is $5\mathrm{.}06{10}^{8}k{m}^2,$ and its crust has a mean thickness of $35\mathrm{.}2km$ and mean density of $2\mathrm{.}79\frac{g}{c{m}^3}.$ The two most abundant elements in the crust are oxygen $,$ where $($:$1t=1000(kg)\}$ and silicon $(2\mathrm{.}70{10}^5\frac{g}{t}),$ and the two rarest non$-$radioactive elements are ruthenium and rhodium, each with an abundance of $(1{10}^{-4}\frac{g}{t}).$ What is the total mass of each of these elements in Earth's crust?

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