a highly risk averse investor is considering adding one additional stock to three stock portfolio to form a four stock portfolio. the three stocks currenntly held all have b$=1\mathrm{.}0$ and a perfect positive correlation with the market. potential new stocks a and b both have expected returns of $15\%$ and both are equally correlated with the market with r$=0\mathrm{.}75.$ stock a SD is $12\%$ and stock b SD is $8\%$

which stock should this investor add to his or her portfolio