workshop produces parts. The monthly plan (1/2) is completed in the first ten days of February, and the monthly plan (1/5) is completed in the middle of February. Exactly 3,500 pieces have been completed. How many pieces are in the monthly plan?
某车间生产零件，二月份上旬完成月计划的(1/2)，中旬再完成月计划的(1/5)正好完成了3500件，求月计划是多少件？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

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

<gadget id="calculator">(1/2) + (1/5)</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">3_500 / (7/10)</gadget>
<output>5_000</output>

<result>5_000</result>