6. Your company produces a favorite summertime food product, and you have been placed in charge of forecasting shipments of this product. The historical data below represent your company's past experience with the product. a. Since the data appear to have both seasonality and trend, you should estimate a Winters" model and calculate its root-mean-squared error. b. You also have access to a survey of the potential purchasers of your product. This information has been collected for some time, and it has proved to be quite accurate for predicting shipments in the past. Calculate the root-mean-squared error of the purchasers' survey data. c. After checking for bias, combine the forecasts in parts (a) and (b) and determine if a combined model may forecast better than either single model. Purchasers' Purchasers' Date Shipments (5000) Survey (5000) Date Shipments ($000) Survey (5000) Apr-2002 13,838.00 13,920 32 Jun-2003 21.056.00 24,644.20 May-2002 15,137.00 15,052 82 Jul-2003 13,509.00 14,224-17 Jun-2002 23,713.00 26,207.69 Aug-2003 9,729.00 9,194.77 Jul-2002 17,141.00 17,237.59 Sep-2003 13,454.00 12,141,25 Aug-2002 7.107.00 7,687 23 Oct-2003 13,426.00 11,971.93 Sep-2002 9.225.00 9.788 06 Nov-2003 17,792.00 17,654.14 Oct-2002 10,950.00 7,889.46 Dec-2003 19,026.00 15.580.19 Nov-2002 14,752.00 14.679.10 Jan-2004 9,432.00 9,961.98 Dec-2002 18,871.00 17.644.48 Feb-2004 6,356.00 7.368 55 Jan-2003 11.329.00 10,436.45 Mar-2004 12,893.00 11,286 25 Feb-2003 6.555.00 6.304.89 Apr-2004 19,379.00 18,915.33 Mar-2003 9,335.00 9.354,44 May-2004 14,542.00 14,056.06 Apr-2003 10.845.00 11.759.15 Jun-2004 18,043.00 20,699.38 May-2003 15,185.00 14,971.57 Jul-2004 10,803.00 12,892.97