Kay is the operation manager for a line of sportswear. She would like to provide a quarterly forecast of sales for the Northern United States. One of her colleagues suggested that unemployment $($NRUR$),$ and income $($INC$)$ in the regions in which the clothes are marketed might be causally connected to sales. To see whether a multiple regression model would work well, she fit the model on a $10-$year quarterly sales history using EXCEL. The partial summary output is given below.