How do I calculate avg inflation rate and T-bill in Excel

How do I calculate this in excel?

You’ve observed the following returns on SkyNet Data Corporation’s stock over the past five years: 13 percent, –13 percent, 20 percent, 25 percent, and 10 percent. Suppose the average inflation rate over this period was 3 percent, and the average T-bill rate over the period was 3.3 percent.