A factory needs to process a batch of parts. It plans to process 120 parts per day, but actually processes 20 more parts per day than planned. As a result, the task is completed 5 days ahead of schedule. How many parts are there in this batch?
某工厂要加工一批零件，计划每天加工120个，实际每天比计划多加工20个，结果提前5天完成任务．这批零件共有多少个？
<gadget id="calculator">120 * 5</gadget>
<output>600</output>

<gadget id="calculator">20 - 120</gadget>
<output>-100</output>

<gadget id="calculator">120 + (-100)</gadget>
<output>20</output>

<gadget id="calculator">600 / 20</gadget>
<output>30</output>

<gadget id="calculator">120 + 20</gadget>
<output>140</output>

<gadget id="calculator">30 * 140</gadget>
<output>4_200</output>

<result>4_200</result>