Reconsider the oxide thickness data in Exercise 7-35 and suppose that it is reasonable to assume that oxide thickness is normally distributed. 

(a) Compute the maximum likelihood estimates of μ and σ².

(b) Graph the likelihood function in the vicinity of μ̂ and σ̂², the maximum likelihood estimates, and comment on its shape.

(c) Suppose that the sample size was larger (n = 40) but the maximum likelihood estimates were numerically equal to the values obtained in part (a). Graph the likelihood function for n = 40, compare it to the one from part (b), and comment on the effect of the larger sample size.