Quarterly Sales
the Quarterly Sales (In Millions of Dollars)of a Department

Quarterly sales
The quarterly sales (in millions of dollars)of a department store chain were recorded for the years 1997-2000.They are listed below. $$\begin{array} { | c | c | c | } \hline \text { Year } & \text { Quarter } & \text { Sales } \\\hline 1997 & 1 & 21 \\& 2 & 36 \\& 3 & 28 \\& 4 & 44 \\1998 & 1 & 25 \\& 2 & 23 \\& 3 & 39 \\& 4 & 36 \\1999 & 1 & 30 \\& 2 & 41 \\& 3 & 47 \\& 4 & 55 \\2000 & 1 & 34 \\& 2 & 29 \\& 3 & 32 \\& 4 & 48 \\\hline\end{array}$$
-Calculate the four-quarter centered moving averages.