The following data report total, monthly U.S. book-store sales in millions of dollars from January 2016 to March 2019. (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.)

Month	2016	2017	2018	2019
January	1618	1536	1421	1294
February	877	841	859	816
March	869	857	884	835
April	859	879	860
May	928	931	936
June	863	854	877
July	837	819	851
August	1674	1524	1514
September	1214	1147	1136
October	865	839	891
November	892	853	918
December	1406	1307	1409

c. Which forecasting model is appropriate based on the data for the total U.S. bookstore sales? Appropriate model = (Regress, Simple exponential smoothing, or Simple moving average)

d. Evaluate a seasonally adjusted trend forecasting model. What is the MAD? (Round your answers to 4 decimal places.)

Month	2016	Trend	Index	Forecast	Absolute Error
January	1618
February	877
March	869
April	859
May	928
June	863
July	837
August	1674
September	1214
October	865
November	892
December	1406
Month	2017
January	1536
February	841
March	857
April	879
May	931
June	854
July	819
August	1524
September	1147
October	839
November	853
December	1307
Month	2018
January	1421
February	859
March	884
April	860
May	936
June	877
July	851
August	1514
September	1136
October	891
November	918
December	1409
Month	2019
January	1294
February	816
March	835

e. What is the average monthly trend in book-store sales? (Negative amounts should be indicated by a minus sign. Round your answer to 4 decimal places.) Ave Monthly trend in book-store sales = ______ mill/per month

f-1. What are the monthly indexes? (Round your answers to 4 decimal places.)

Month	Index
1
2
3
4
5
6
7
8
9
10
11
12

f-2. Which month are book sales the highest?

f-3. Which month are book sales the lowest?

g. Predict book sales for the next 9 months. (Round your answers to 4 decimal places.)

Year	Month	Forecast Sales
2019	April
2019	May
2019	June
2019	July
2019	August
2019	September
2019	October
2019	November
2019	December