Master Chen processed a batch of parts. In the first 2 hours, he processed 18 pieces per hour. He found that if he continued to do so, he would finish the task 4 hours later than the stipulated time; so he sped up the progress and processed 4 more pieces per hour. , As a result, the task was completed 2 hours ahead of schedule. How many parts are there in this batch?
陈师傅加工一批零件，开始的2小时，他每小时加工18个，他发现照这样做下去，要比规定完成任务的时间推迟4小时做完；于是加快了进度，每小时多加工4个，结果提前2小时完成任务，这批零件有多少个？
<gadget id="calculator">18 * 4</gadget>
<output>72</output>

<gadget id="calculator">18 * 2</gadget>
<output>36</output>

<gadget id="calculator">4 * 2</gadget>
<output>8</output>

<gadget id="calculator">8 - 36</gadget>
<output>-28</output>

<gadget id="calculator">72 + 36 + 36 + 8 + (-28)</gadget>
<output>124</output>

<gadget id="calculator">4 - 18</gadget>
<output>-14</output>

<gadget id="calculator">18 + (-14)</gadget>
<output>4</output>

<gadget id="calculator">124 / 4</gadget>
<output>31</output>

<gadget id="calculator">31 + 4</gadget>
<output>35</output>

<gadget id="calculator">18 * 35</gadget>
<output>630</output>

<result>630</result>