$($Expected rate 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 the risk $($as measured by the standard deviation$)$ and return?

$\backslash$table$[[$Common Stock A$,$Common Stock B$],[$Probability$,$Return,Probability,Return$],[0\mathrm{.}20,13\%,0\mathrm{.}15,-4\%$