Problem 8-7 Portfolio risk and return Here are returns and standard deviations for four investments. Return Standard Deviation Treasury bills Stock P Stock 0 Stock R 5.0 10.0 16.0 23.5 8 12 28 26 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 94 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 96 Perfect positive correlation Perfect negative correlation No correlation % 96