Let

$$f(x)=\begin{cases} px+2 & \text{if } 0 \leq x < 2 \\ 7-qx & \text{if } 2 \leq x < 4 \\ 2x+1 & \text{if } 4 \leq x < 6 \end{cases}\text{.}$$

Find $p$ and $q$ such that $f$ is continuous.