Let $$f(x) = x^5 + 2e^{x/4}$$ for all $$x \in R$$. Consider a function g(x) such that $$(g \circ f)(x) = x$$ for all $$x \in R$$. Then the value of $$8g'(2)$$ is:

A

$$2$$

B

$$8$$

C

$$4$$

D

$$16$$