We're going to build a new function F from an old one f using function composition. Specifically, we're going to compose x⁸ into f. So our function is F(x)=f(x⁸) and we're evaluating at x=a.
a) F(a) = f(a⁸)
b) F(a) = f(a)⁸
c) F(a) = f(a)⁸
d) F(a) = f⁸(a)