With reference to following Calculations, compare and contrast the Return and Risk of Portfolio $1$ with Portfolio $2.$ Which is considered to be more efficient? Identify potential factor$($s$)$ that cause one portfolio to be more efficient than the other. $($Both portfolios are made up of $50\%$ of both assets$)\backslash$table$[[,$NAB,CBA,Portfolio $1],[$Monthly mean,$1\mathrm{.}75\%,2\mathrm{.}11\%,1\mathrm{.}93\%],[$Month$1$y variance,$0\mathrm{.}35\%,0\mathrm{.}19\%,0\mathrm{.}22\%],[$Monthly standard deviation,$5\mathrm{.}92\%,4\mathrm{.}30\%,4\mathrm{.}73\%]]$

$\backslash$table$[[,$NAB,CBA,Portfolio $1],[$Annual mean,$20\mathrm{.}99\%,25\mathrm{.}35\%,23\mathrm{.}17\%],[$Annual variance,$4\mathrm{.}20\%,2\mathrm{.}22\%,2\mathrm{.}68\%],[$Annual standard deviation,$20\mathrm{.}51\%,14\mathrm{.}91\%,16\mathrm{.}39\%]]$

$\backslash$table$[[,$NAB,QAN,Portfolio $2],[$Month$1$y mean,$1\mathrm{.}75\%,2\mathrm{.}02\%,1\mathrm{.}88\%],[$Month$1$y variance,$0\mathrm{.}35\%,1\mathrm{.}26\%,0\mathrm{.}46\%],[$Monthly standard deviation,$5\mathrm{.}92\%,11\mathrm{.}21\%,6\mathrm{.}76\%]]$

$\backslash$table$[[,$NAB,QAN,Portfolio $2],[$Annual mean,$20\mathrm{.}99\%,24\mathrm{.}25\%,22\mathrm{.}62\%],[$Annual variance,$4\mathrm{.}20\%,15\mathrm{.}08\%,5\mathrm{.}48\%],[$Annual standard deviation,$20\mathrm{.}51\%,38\mathrm{.}84\%,23\mathrm{.}42\%]]$