# title
## subtitle
\begin{align}
s(x)=\begin{cases}
-4x+31& \text{ if } 0\le x \le 12\\
295& \text{ if } 12< x \le 20\\
\frac{4}{3}x+278.5& \text{ if } 20< x \le 30\\
\frac{3}{2}x+404& \text{ if } 30< x <40\\
\end{cases}
\end{align}
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