$7-7.($Calculating expected rates of return and risk$)$ Syntex, Inc., is considering an investment in one of two common stocks. Given the information that follows, which investment is better, based on risk $($as measured by the standard deviation$)$ and return?

$\backslash$table$[[$Common Stock A$,$Common Stock B$],[$Probability$,$Return,Probability,Return$],[\mathrm{.}30,11\%,\mathrm{.}20,-5\%$