unable to fojd the roght ecel formula to solve this. Can inget help please?

9. Suppose that you work for a major U.S. retail department store that has outlets nationwide. The store offers credit to customers in various forms, including store credit cards, and over the years has seen a substantial increase in credit purchases. The manager of credit sales is concerned about the degree to which consumers are using credit and has started to track the ratio of consumer installment credit to personal income. She calls this ratio the credit percent, or CP, and has asked that you forecast that series for year 8. The available data are: (c1p9 [) a. Use the first naive model presented in this chapter to prepare forecasts of CP for years 2 through 8. b. Plot the actual and forecast values of the series for the years 1 through 8 . (You will not have an actual value for year 8 or a forccast value for year I.) b. Plot the actual and forecast values of the series for the years 1 through 8 . (You will not have an actal value for year 8 or a forecest value for year I.) c. Caleulare the MAIV for youa forecast for yeas 2 tifeciph 7