based on the captial asset pricing model $($CAPM$)$ which of the following should earn the highest risk premium? a$)$ diversified portfolio with returns similar to the overall market b$)$ stock with beta of $1\mathrm{.}24$ c$)$ stock with a beta of $\mathrm{.}63$ d$)$ US treasury bill e$)$ portfolio with a beta of $1\mathrm{.}12$