Joint MLEs in a Normal Model

Suppose $X_1,\dots,X_9$ are modeled as i.i.d. $N(\mu,\sigma^2)$. From the sample you know that $$\bar X = 5, \qquad \sum_{i=1}^9 (X_i-\bar X)^2 = 18.$$ Find the MLEs of $\mu$ and $\sigma^2$.