Table P-9 contains a time series of 80 observations. Using a computer program for ARIMA modeling, obtain a plot of the data, the sample autocorrelations, and the sample partial autocorrelations. Develop an appropriate ARIMA model, and generate forecasts for the next three time periods from forecast origin t = 80.

TABLE P.9 1 21 50 41 9 6 57 2 50 22 9 42 49 62 56 3 62 23 53 43 64 63 53 4 47 24 57 44 554 5 5 64 25 52 45 48 65 55 6 40 2 66 46 6 66 66 7 76 27 47 47 4767 49 8 38 28 67 48 58 68 57 75 29 5149 4669 50 10 4 30 5750 58 70 68 74 31 5551 5771 42 12 47 32 64 52 52 72 77 72 33 48 53 62 73 30 14 47 34 6554 46 74 88 15 62 35 52 55 72 75 37 57 36 65 56 37 76 88 17 56 37 47 57 777 32 18 53 38 68 58 33 7890 19 58 39 4859 71 79 31 20 61 40 6 60 47 80 85