Total Cost Over a Negative-Binomial Horizon

Let $X_1,X_2,\dots$ be i.i.d. increments with $E[X_i]=4$ and $\mathrm{Var}(X_i)=6$. Let $N$ be independent of the increments and distributed as NegativeBinomial(r=3, p=\frac{2}{5}). For the stopped sum $S_N=\sum_{i=1}^N X_i$, compute $E[S_N]$ and $\mathrm{Var}(S_N)$.