XYZ$,$ Inc. has a beta of $0\mathrm{.}8.$ The yield on a $3-$month T$-$bill is $4\%,$ and the yield on a $10-$year T$-$bond is $6\%.$ The market risk premium is $5\mathrm{.}5\%,$ and the return on an average stock in the market last year was $15\%.$ What is the estimated cost of common equity using the CAPM?