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Year 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1 72.962 145.592 153.907 176.076 202,415 174,200 253, 142 257,156 289,321 313,769 Sales 2 81.921 117.129 100.144 180.440 211,780 182,556 218,755 202,568 266.095 315.011 3 97.729 114.159 123.242 162.665 163,710 198,990 225,422 224,482 262,938 264,939 142.161 151.402 128.497 220.818 200,135 243,700 253,653 229,879 322.052 301.479 a) b) c) d) Prepare a time-series plot of the data, and on the basis of what you see in the plot, write a brief paragraph in which you explain what patterns you think are present in the sales series. Smooth out seasonal influences and irregular movement by calculating the center moving averages. Add the centered moving averages to the original data you plotted in part a. Has the process of calculating center moving averages been effective in smoothing out the seasonal and irregular fluctuations in the data? Explain. Determine the degree of seasonality by calculating seasonal indexes for each quarter of the year. Develop a forecast for Ms Lynch for the four quarters of 1998.