Continuity of a Piecewise Function

Let $z$ be the function defined below, where $c$ is a constant. For what value of $c$ is $z$ continuous at $x=3$?

$\displaystyle z(x) = \begin{cases} \displaystyle x\sin\left(\frac{\pi x}{3}\right) & \text{for } x < 3 \\ \displaystyle c\sqrt{x-2} + 2 & \text{for } x \geq 3 \end{cases}$