Given the following information for a listed company, the expected return if invested in the shares of this company is $7\mathrm{.}80\%.$ Calculate the variance and the standard deviation of this expected return.Given the following information for a listed company, the expected return if invested in the shares of this company is $7.80\%.$ Calculate the variance and the standard deviation of this expected return.$|$

$(3)$

$\backslash$table$[[$State of Economy,Probability,Percentage Return$],[$State $1,0\mathrm{.}30,13\%],[$State $2,0\mathrm{.}35,8\%],[$State $3,0\mathrm{.}15,2\%],[$State $4,0\mathrm{.}20,4\%]]$