The data file Quarterly Earnings shows quarterly sales of a corporation over a period of 6 years. Use the Holt-Winters seasonal method to obtain forecasts of sales up to eight quarters ahead. Employ...

The data file
Quarterly Earnings
shows quarterly sales of a corporation over a period of 6 years. Use the Holt-Winters seasonal method to obtain forecasts of sales up to eight quarters ahead. Employ smoothing constants a = 0.4, b = 0.5, and g = 0.6. Graph the data and the forecasts.