Which is correct and most complete (within the implied uncertainty)?

a. A full quadratic polynomial cannot be fitted since (X′X)–1X′ is undefined.

b. RSM fitted coefficients are 5.88, 1.83, 0.19, 0.25, 0.06, and 2.75.

c. RSM fitted coefficients are 5.88, 2.83, 0.19, 0.25, 1.06, and 2.75.

d. All of the above are correct.

e. All of the above are correct except

(a) and (d).