Quarterly Billing for Water Usage Is Shown Below AFind the Seasonal Index for Each Quarter

Essay

Quarterly billing for water usage is shown below. $$\begin{array} { c | r r r r } & { \text { Year } } \\\text { Quarter } & 1 & { 2 } & { 3 } & { 4 } \\\hline \text { Winter } & 64 & 66 & 68 & 73 \\\text { Spring } & 103 & 103 & 104 & 120 \\\text { Summer } & 152 & 160 & 162 & 176 \\\text { Fall } & 73 & 72 & 78 & 88\end{array}$$
a.Find the seasonal index for each quarter.
b.Deseasonalize the data.
c.Find the trend line.
d.Assume there is no cyclical component and forecast the summer billing for year 5.