8-1 Here are returns and standard deviations for four investments. Return Standard Deviation Treasury bills 4.0 % 0 % Stock P 12.0 11 Stock Q 13.0 28 Stock R 22.0 22 Required: Calculate the standard deviations of the following portfolios. (Round your answers to 1 decimal place. Omit the "%" sign in your response.) (a) 50% in Treasury bills, 50% in stock P. Standard deviation % (b) 50% each in Q and R, assuming the shares have