9. In our country, individual income tax on wages and salaries is calculated in segments. Total income not exceeding 800 yuan is exempt from individual income tax on wages and salaries; the portion exceeding 800 yuan is subject to taxation. Let the taxable amount for the entire month be $x$, where $x=$ total monthly income - 800 yuan. The tax rates are as follows:
\begin{tabular}{|c|c|c|}
\hline Level & Monthly taxable amount $x$ & Tax \\
\hline 1 & Up to 500 yuan \\
\hline 2 & Over 500 yuan to 2000 yuan & $5 \%$ \\
\hline 3 & Over 2000 yuan to 5000 yuan & $10 \%$ \\
\hline$\vdots$ & & $15 \%$ \\
\hline 9 & Over 100000 yuan & $45 \%$ \\
\hline
\end{tabular}
(1) If the tax amount is $f(x)$, try to express the calculation formula for the tax amount $f(x)$ of levels 1-3 using a piecewise function.
(2) A person's total monthly income in March 2000 was 3000 yuan. Calculate how much personal income tax this person should pay in March.
9. (1) \( f(x)=\left\{\begin{array}{ll}5\% \cdot x & 0<x \leqslant 500 \\ 10\% \cdot(x-500)+500 \times 5\% & 500<x \leqslant 2000 \\ 15\% \cdot(x-2000)+1500 \times 10\%+500 \times 5\% & 2000<x \leqslant 5000\end{array}\right. \)
(2) \( x=3000-800=2200, 2000<2200<5000, f(2200)=15\% \times(2200-2000)+1500 \times 10\%+500 \times 5\%=205 \) yuan.