Number of triangles in an $(n, n / 2,2 \sqrt{n})$-expander

Question

Prove that for every $\epsilon>0$ there exists an $n_{0}=n_{0}(\epsilon)$ so that for every $(n, n / 2,2 \sqrt{n})$ - graph $G=(V, E)$ with $n>n_{0}$, the number of triangles $M$ in $G$ satisfies $\left|M-n^{3} / 48\right| \leq \epsilon n^{3}$

Reference "The probabilistic method" by Alon and Spencer 3rd 9.4.4