Which is correct and most complete?

a. The model form in

(c) in Table 13.19 contains one interaction term.

b. Using the design matrix and model in

(a) and

(b) in Table 13.19, X′X is diagonal.

c. Using the design matrix and model in

(a) and

(c) in Table 13.19, X′X is diagonal.

d. All of the above are correct.

e. All of the above are correct except

(a) and (d).