Chapter 4.8, Problem 57E

Sales The table shows the average sales S (in millions of dollars) of an outerwear manufacturer for each month t, where $t=1$ corresponds to January.

Time, t	1	2	3	4
Sales, S	13.46	11.15	8.00	4.85

Time t	5	6	7	8
Sales, S	2.54	1.70	2.54	4.85

Time t	9	10	11	12
Sales, S	8.00	11.15	13.46	14.30

(a) Create a scatter plot of the data.

(b) Find a trigonometric model that fits the data. Graph the model with your scatter plot. How well does the model fit the data?

(c) What is the period of the model? Do you think it is reasonable given the context? Explain.

(d) Interpret the meaning of the model's amplitude in the context of the problem.