A portfolio comprises Coke $($beta of $1\mathrm{.}1)$ and Wal$-$Mart $($beta of $0\mathrm{.}9).$ The amount invested in Coke is $$10,000$ and in Wal$-$Mart is $$20,000.$ What is the beta of the portfolio?

A$.0\mathrm{.}87$

B$.1\mathrm{.}02$

C$.0\mathrm{.}97$

D$.1\mathrm{.}06$