The file S12_56.xlsx contains monthly time series data for total U.S. retail sales of building materials (which includes retail sales of building materials, hardware and garden supply stores, and mobile home dealers). Does a regression approach for estimating seasonality provide forecasts that are as accurate as those provided by (a)Winters’ method and (b) the ratio-to-moving-average method? Compare the summary measures of forecast errors associated with each method for de-seasonalizing the given time series. Summarize the results of these comparisons.