Assume that portfolios A and $B$ are both well diversified and that $E(r_A)=20\%,$ and $E(r_B)=15\%.$ If the economy has only one factor, and ${?}^6{A}_A=1\mathrm{.}3,$ whereas $B_B=0\mathrm{.}8,$ what must be the risk$-$free rate?

Note: Do not round intermediate calculations. Round your answer to two decimal places.

Risk$-$free rate

$\%$