Let $X_{1}, \ldots, X_{n}$ be independent Poisson trials such that $\operatorname{Pr}\left(X_{i}\right)=p_{i}$. Let $X=\sum_{i=1}^{n} a_{i} X_{i}$ and $\mu=\mathbf{E}[X]$. Use the result of Exercise $4.15$ to prove that, for any $0<\delta<1$
$$
\operatorname{Pr}(|X-\mu| \geq \delta \mu) \leq 2 \mathrm{e}^{-2 \delta^{2} \mu^{2} / n}
$$