9. The individual income tax on wages and salaries in our country 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:
（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.