You own a stock portfolio invested $20$ percent in Stock Q$,25$ percent in Stock R$,25$ percent in Stock S$,$ and $30$ percent in Stock T$.$ The betas for these four stocks are $1\mathrm{.}6,0\mathrm{.}5,1\mathrm{.}7,$ and $0\mathrm{.}9,$ respectively. What is the portfolio beta?