Differentiation

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