Let f(x)=x^5+2 e^x / 4 for all x ∈ R. Consider a function g(x) such that (g ° f)(x)=x for all x ∈ R. Then the value of 8 g^′(2) is:

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