The following data show the quarterly sales of the 6x* tents for three years at a sporting goods store. The store owner wants to forecast the quarterly sales for the next year. (a) Construct a time series plot. What type of pattern exists in the data? (b) Use dummy variables and the Excel Regression tool to find a multiple regression model that accounts for seasonal effects in the data. (c) Based on this model, estimate the quarterly sales for the fourth year. D 3 4 5 Year 6 8 1 1T 1 1 2 222 m m m m Quarter 3 3 3 3 PAKE 12 341N3 2 41234 Q1 1 0 0 0 1 0 0 0 HOOO 0 Q2 0 100 0 1 0 OOHOO 0 0 1 0 0 Q3 OOHOOOOOOO 0 0 0 Sales 71 49 58 78 68 41 60 81 55 48 62 80