Professor Wang's monthly salary is 9,000 yuan. According to national regulations, after deducting 3,500 yuan from the total salary, the individual income tax is paid at 20%. How much is the personal income tax that Professor Wang should pay every month?
王教授的月工资是9000元，按照国家规定，工资总额减去3500元后，按照20%交纳个人所得税，王教授每月应交个人所得税多少元？
<gadget id="calculator">9_000 - 3_500</gadget>
<output>5_500</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">5_500 * (1/5)</gadget>
<output>1_100</output>

<result>1_100</result>