What is the Standard deviation fo returns for each stock given below information?

And what is the standard deviation of returns for a portfolio comprising 60 % of Stock A and 40 % of Stock B?

9. Consider the two (excess return) multi-factor model regression results for A and B: RA = 2% + 1.3RM + 0.8RSMB + eA RB = 1% + 1.5RM + 1.2RSMB + eB OM = 22%; OSMB = 25%; R-squareA = 0.5; R-squares = 0.7 a) What is the standard deviation of returns for each stock? b) What is the standard deviation of returns for a portfolio comprising 60% of Stock A and 40% of Stock B