Here are returns and standard deviations for four investments. Return Standard Deviation Treasury bills Stock P Stock Q Stock R 6.0 10.5 18.0 21.0 0 10 26 25 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 % %