The following data report total, monthly U.S. book-store sales in millions of dollars from January 2019 to December 2021. (Go to https://www.census.gov/retail/index.html#mrts, find “Monthly Retail Trade Report,” then select “Time Series/Trend Charts” to find the data for the total U.S. bookstore sales.)

a. Graph the data.b. Based on the graph, describe the time series pattern.c. For this time series, why is forecasting with a seasonally adjusted trend model appropriate?d. Evaluate a seasonally adjusted trend forecasting model. What are the MAD and MAPE?e. What is the average monthly trend in book-store sales?f. What are the monthly indexes? When are book sales the highest? When are book sales the lowest?g. Predict book sales for the next 9 months.h. In your judgment, are the forecasts “good”? What disclaimer would you include with your forecast?

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Month January February March April May June July August September October November December 2019 $1,029 585 603 650 696 613 591 1,124 871 650 640 1,074 Year 2020 $990 593 406 169 275 388 437 770 620 455 496 900 2021 $820 459 547 514 632 703 712 1,154 883 697 708 1,203