Which is correct and most complete according to the text?

a. The concept of a method rollercoaster emphasizes individual expertise levels.

b. Optimization has not yet been used to produce methods or strategies.

c. The nature of six sigma projects places no restriction on relevant test beds.

d. Six sigma databases can help predict the costs in future projects.

e. All of the above are correct.

f. All of the above are correct except

(a) and (e).