Suppose that you invest $60\%$ in Stock A and $40\%$ in Stock B$.$ The standard deviation of A is $23\%,$ and that of B is $34\%.$The correlation between the returns of A and B is $0\mathrm{.}26.$ Calculate the portfolio standard deviation. The answer should be given in decimal form $($e$.$g$.,$ if $10\%$ is the correct answer, write $0\mathrm{.}10,$ NOT $10\%).$