I have to solve it on excel.

After tallying the receipts for their first year of operation, the owners of the Taco Barn are encouraged. Sales of their artisanal tacos, made from such exotic ingredients as ground beef, cheese, and beans, have been strong and seem to give hope to the coming year. Taco sales by month are shown in the table.

Month	Sales
January	474
February	485
March	501
April	588
May	579
June	673
July	594
August	679
September	608
October	699
November	732
December	732

The manager is open to suggestions for forecasting models and decides to try both a linear trend model and an exponential smoothing model with an alpha of 0.9. Generate forecasts for the year using these techniques and then calculate forecast errors using MAD to determine which is the superior method in this scenario.