Linlin's father received a labor fee of 4,200 yuan. Among them, 800 yuan is tax-free, and the rest is taxed at a rate of 20%. How much tax will be paid for this service fee?
琳琳的爸爸得到一笔4200元的劳务费．其中800元是免税的，其余部分按20%的税率缴税，这笔劳务费用一共要缴税多少元？
<gadget id="calculator">4_200 - 800</gadget>
<output>3_400</output>

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

<gadget id="calculator">3_400 * (1/5)</gadget>
<output>680</output>

<result>680</result>