Dad's monthly salary is 4,000 yuan. According to the regulations, the portion exceeding 3,500 yuan is subject to personal income tax at a rate of 3%. How much personal income tax should Xiao Ming's father pay every month?
爸爸每月的工资是4000元，按规定超过3500元部分按3%的税率缴纳个人所得税，小明的爸爸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">3 / 100</gadget>
<output>3/100 = around 0.03</output>

<gadget id="calculator">500 * (3/100)</gadget>
<output>15</output>

<result>15</result>