Total PnL Until a Geometric Number of Fills

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