9. Calculating Returns and Variability You've observed the following returns on Mary Ann Data Corporation's stock over the past five years: 27 percent, 13 percent, 18 percent, -14 percent, and 9 percent. a. What was the arithmetic average return on Mary Ann's stock over this five-year period? b. What was the variance of Mary Ann's returns over this period? The standard deviation? 10. Calculating Real Returns and Risk Premiums In Problem 9, suppose the average inflation rate over this period was 4.2 percent, and the average T-bill rate over the period was 5.1 percent. a. What was the average real return on Mary Ann's stock? b. What was the average nominal risk premium on Mary Ann's stock