Need calculations on how to solve for question 10 based on question 9. Thank you

9. Calculating Returns and Variability [LO1] Youve observed the following returns on Crash-n-Burn Computer's stock over the past five years: 7percent, -13 percent, 21 percent, 34 percent and 15 percent.

a. What was the arithmetic average return on Crash-n-Burn's stock over this five year period?

b. What was the variance of Crash-n-Burn's returns over this period? The standard deviation?

10. Calculating Real Returns and Risk Premiums [LO1] For problem 9, suppose the average inflation rate over this period was 3.5 percent and the average T-bill rate over the period was 4.2 percent.

a. What was the average real return on Crash-n-Burn's stock?

b. What was the average nominal risk premium on Crash-n-Burn's stock?