Fourth moment of a normal mixture

Let $X$ be a random variable having the probability density function $$f(x)=\frac{1}{8\sqrt{2\pi}}\left(2e^{-\frac{x^{2}}{2}}+3e^{-\frac{x^{2}}{8}}\right),\quad-\infty<x<\infty.$$ Then, $4E\left(X^{4}\right)$ is equal to __________.