Uncle Zhang’s total salary income in January is 4,200 yuan, and the part exceeding 3,500 yuan is taxed at 3%. How much tax should Uncle Zhang pay in January?
张叔叔一月份的工资总收入是4200元，超出3500元的部分按3%缴税，张叔叔一月份应缴税多少元．
<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>

<result>21</result>