Dad's monthly salary is 4,200 yuan. According to regulations, the part of the monthly salary income exceeding 3,500 yuan should be paid personal income tax at a rate of 3%. How much is Dad's monthly after-tax salary?
爸爸每月工资为4200元，按规定，月工资收入超过3500的部分，应按3%的税率缴纳个人所得税．爸爸每月实得税后工资多少元？
<gadget id="calculator">4_200 - 3_500</gadget>
<output>700</output>

<gadget id="calculator">3 / 100</gadget>
<output>3/100 = around 0.03</output>

<gadget id="calculator">700 * (3/100)</gadget>
<output>21</output>

<gadget id="calculator">4_200 - 21</gadget>
<output>4_179</output>

<result>4_179</result>