Consider a stock with beta equal to $1\mathrm{.}5,$ a risk$-$free rate of $3\%,$ and a market return of $10\%.$ What is the expected return of the stock using CAPM?

We have $10$ stocks with the same standard deviation of $20\%.$ Assume CAPM market beta captures all undiversifiable risk.

a$.$ If all $10$ stocks all have zero market beta, what is the standard deviation of an equally$-$weighted portfolio of these $10$ stocks?

b$.$ If all $10$ stocks all have a market beta of $1,$ what is the standard deviation of an equally$-$weighted portfolio of these $10$ stocks?