Refer to Exercise 12-9 and the corresponding data shown in Table 12-13.

(a) Based on a scatterplot of order fulfillment time versus order value, you decide to fit a quadratic model in order value. What is the model equation?

(b) What are values of R2 and R2a?

(c) Test if adding a quadratic term in value is useful. Use α =0.05.

(d) Find a 95% confidence interval for the mean fulfillment time if the order value is

$75,000.Howdoes this compare to the interval obtained inExercise 12-10, part (a)?