Here are returns and standard deviations for four investments Standard Deviation (%) Treasury bills Stock P Stock Q Stock R Return(%) 3.5 11.5 13.5 23.5 18 35 28 Calculate the standard deviations of the following portfolios a. 50% in Treasury bills, 50% in stock P. (Do not round intermediate calculations. 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