Uncle Li's monthly salary is 4,000 yuan. According to the personal income tax law, after deducting 3,500 yuan from his monthly income, he pays tax at 5%. How much personal income tax should Uncle Li pay every month?
李叔叔月工资4000元，按个人所得税法规定，每月收入扣除3500元后按5%交税．李叔叔每月应缴纳个人所得税多少元？
<gadget id="calculator">4_000 - 3_500</gadget>
<output>500</output>

<gadget id="calculator">5 / 100</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">500 * (1/20)</gadget>
<output>25</output>

<result>25</result>