Consider COGS.xlsx. Apply the following forecasting methods to forecast two years: Implement each model in a separate spreadsheet.

1. Plot the data. How would you describe the data in terms of seasonality and trend?
2. Moving average using k =12.
3. Weighted moving average using k =12 (find w_i using solver)
4. Exponential Smoothing (find using solver)
5. Stationary Additive seasonal effect (find and using solver)
6. Stationary Multiplicative seasonal effect (find and using solver)
7. Double moving average (k=12)
8. Holt's method
9. Holt-Winter's method for additive seanonal
10. Holt-Winter's method for multiplicative seanonal
11. Seasonal Regression
12. Which model is the best for this dataset? Compare each method based on MSE.