The sales data for two years are as follows. Data are aggregated with two months of sales in each "period."

a$.$ Plot the data.

Instructions:

Click the "Sales" line segment icon at the top right of graph.

Move your cursor to the approximate location for the first data point $(x=1,y=$ first sales value$).$ Left click to insert the

point. Release the left mouse button.

Move your cursor to the approximate location for the second data point. Left click to insert the point $($a line segment

will automatically connect this new point to the previous point$).$ Release the left mouse button.

Repeat the above step for the remaining data points.

Click anywhere on the line segment between two points. A gear icon should appear. Click it to open the "line

properties" window.

Enter the exact coordinates for all $12$ points. Click $"$ok$"$ when finished.

b$.$ Fit a simple linear regression model to the sales data.

Note: Do not round intermediate calculations. Round your final answers to $2$ decimal places.

$Y=$

In addition to the regression model, determine multiplicative seasonal index. A full cycle is assumed to be a full year.

Note: Do not round intermediate calculations. Round your and final answers to $2$ decimal places.

d$.$ Prepare sales forecasts for next year using both of your regression models derived above to show results both with and

without adjustments for seasonality.

Note: Do not round intermediate calculations. Round your final answers to $1$ decimal places.