#### Answer

The Power Rule applies to
(a), (c) and (f).

#### Work Step by Step

(a) since $ f(x)=x^2$ is of the form $ x^n $, then the Power Rule does apply to find $ f'(x)$
(b) since $ f(x)= 2^2$ is not of the form $ x^n $, then the Power Rule does not apply.
(c) since $ f(x)=x^e $ is of the form $ x^n $, then the Power Rule does apply to find $ f'(x)$
(d) since $ f(x)= e^x $ is not of the form $ x^n $, then the Power Rule does not apply.
(e) since $ f(x)= x^x $ is not of the form $ x^n $, then the Power Rule does not apply.
(f) since $ f(x)=x^{-4/5}$ is of the form $ x^n $, then the Power Rule does apply to find $ f'(x)$