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-Year	2016	2017	2018	2019
January	1,618	1,536	1,421	1,294
February	877	841	859	816
March	869	857	884	835
April	859	879	860
May	928	931	937
June	863	854	877
July	837	819	851
August	1,674	1,524	1,514
September	1,214	1,147	1,136
October	865	839	891
November	892	853	918
December	1,406	1,307	1,409

c. Which forecasting model is appropriate based on the data for the total U.S. bookstore sales? Regression Analysis / Simple Exponential Smoothing / Simple Moving Average

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

Month Number	$ Sales (Millions)	Period	Trend	Index	Forecast	Absolute Error
1	1,618	1
2	877	2
3	869	3
4	859	4
5	928	5
6	863	6
7	837	7
8	1,674	8
9	1,214	9
10	865	10
11	892	11
12	1,406	12
1	1,536	13
2	841	14
3	857	15
4	879	16
5	931	17
6	854	18
7	819	19
8	1,524	20
9	1,147	21
10	839	22
11	853	23
12	1,307	24
1	1,421	25
2	859	26
3	884	27
4	860	28
5	937	29
6	877	30
7	851	31
8	1,514	32
9	1,136	33
10	891	34
11	918	35
12	1,409	36
1	1,294	37
2	816	38
3	835	39

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.)

Average monthly trend in book-store sales ____ million dollars 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. When are book sales the highest? The month that book sales the highest is ____.

f-3. When are book sales the lowest? The month that book sales the lowest is ____.

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