Three differentiable functions are defined by
I. y=(x−3)3+2
II. y=3(x−3)2
III. y=6(x−3)
Exactly one of the three is a twice-differentiable function f, and the other two are its first and second derivatives. Which choice correctly identifies f, f′, and f′′?
a) I is f′, II is f′′, III is f
b) I is f′′, II is f′, III is f
c) I is f, II is f′, III is f′′
d) I is f, III is f′, II is f′′