Question 3 : The following is the quarterly sales of Pineapple mobile phones for the years 2017 through 2020. The sales are reported in millions of dollars.

Year	Quarter	Sales
2017	1	5,038
	2	3,020
	3	6,600
	4	7,425
2018	1	6,335
	2	1,945
	3	6,781
	4	7,963
2019	1	6,548
	2	2,360
	3	6,954
	4	7,971
2020	1	6,896
	2	2,430
	3	6,702
	4	8,901

a.) Compute the four-quarter centred moving averages for the sales data.

b.) Compute the exponential smoothing with the smoothing constant w = 0.4 for the sales data.

c.) Plot the sales, the four-quarter centred moving average obtained in (a), and the exponential smoothing obtained in (b) against the time

period.

d.) What can you conclude from the original and the smoothed sales data shown in the graph?

e.) Which smoothing method, (a) or (b), is more suitable for smoothing the sales data? Explain your answer.