portfolio's return?

$E(R)$ of $p=rf+b^{**}(Rm-rf)=4\mathrm{.}5\%+1\mathrm{.}05**(10\mathrm{.}2\%-4\mathrm{.}5\%)=10\mathrm{.}5\%$

Assume the portfolio's return is $10\mathrm{.}5\%,$ the market rate is $10\mathrm{.}2\%,$ what's the risk free rate?

$E(R)$ of $p=rf+b^{**}(Rm-rf)$

$10\mathrm{.}5\%=rf+1\mathrm{.}05**(10\mathrm{.}2\%-rf)$