A workshop planned to produce 4200 parts in March, and completed the plan (3/5) in the first half of the month. According to this calculation, how many more parts were actually produced than the original plan.
某车间3月份计划生产4200个零件，上半月就完成了计划的(3/5)，照这样计算，实际比原计划增产多少个．
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(3/5) * 2</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">(6/5) - 1</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">4_200 * (1/5)</gadget>
<output>840</output>

<result>840</result>