Here are returns and standard deviations for four investments. Standard Deviation Return (%) (%) Treasury bills 6.0 Stock P 9.5 14. Stock Q 16.0 25 Stock R 21.5 27 Calculate the standard deviations of the following portfolios a. 50% in Treasury bills, 50% in stock P. (Enter your answer as a percent rounded to 2 decimal places.) % Standard deviation b. 50% each in Q and R, assuming the shares have: (Do not round intermediate calculations. Enter your answers as a percent rounded to 2 decimal places.) Standard Deviation Perfect positive correlation Perfect negative correlation No correlation %