Consider the following stock price returns for Costco and Capital One. Demonstrate all your work.

$\backslash$table$[[$YEAR$.,$COSTCO.,CAPITAL ONE$],[\backslash$table$[[1,0\mathrm{.}47,0\mathrm{.}26],[2,-0\mathrm{.}54,0\mathrm{.}15],[3,0\mathrm{.}15,-0\mathrm{.}14],[4,0\mathrm{.}07,-0\mathrm{.}15],[5,-0\mathrm{.}28,0\mathrm{.}02],[6,0\mathrm{.}4,-0\mathrm{.}18],[7,0\mathrm{.}17,0\mathrm{.}42],[8,-0\mathrm{.}23,0\mathrm{.}3],[9,-0\mathrm{.}04,-0\mathrm{.}32],[10,0\mathrm{.}75,0\mathrm{.}28]],,]]$

a$)$ Calculate the average return and risk of each of them.

b$)$ If the returns follow a normal distribution, what is the probability that Walmart's returns are between $6\%$ and $8\%?$

c$)$ Build a set of portfolios with these returns, calculate their return, risk, construct the efficient frontier graph and select a portfolio, explain your selection.