An appraiser collected the data found in file dat9-18.xlsx that accompanies this book describing the auction selling price, diameter (in inches), and item type of several pieces of early 20th century metal tableware manufactured by a famous artisan. the item type variable is coded as follows: b bowl, c casserole pan, d = dish, t = tray, and p = plate. the appraiser wants to build a multiple regression model for this data to predict average selling prices of similar items. a. construct a multiple regression model for this problem. what is the estimated regression function? b. interpret the value of the r2 statistic for this model. c. construct an approximate 95% prediction interval for the expected selling price of an 18-inch diameter casserole pan. interpret this interval. d. what other variables not included in the model might explain the remaining variation in auction selling prices for these items?