Master Zhang produced a batch of parts. When the statistician asked about the production situation, Master Zhang replied: "The completed quantity is two-fifths of the unfinished ones, and 600 more parts are just one-third of the completed task." How many parts were completed?
张师傅生产一批零件，当统计员问生产情况时，张师傅回答说："已完成的数量是没完成的五分之二，再生产600个正好完成任务的三分之一"，张师傅已经完成了多少个零件？
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">5 + 2</gadget>
<output>7</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">(1/3) - (2/7)</gadget>
<output>1/21 = around 0.047619</output>

<gadget id="calculator">600 / (1/21)</gadget>
<output>12_600</output>

<gadget id="calculator">12_600 * (2/7)</gadget>
<output>3_600</output>

<result>3_600</result>