Master Kong processed a batch of parts. After processing 720 parts, his work efficiency increased by 20%. As a result, the task was completed 4 days ahead of schedule. How many parts are there in this batch?
康师傅加工一批零件，加工720个之后，他的工作效率提高了20%，结果提前4天完成任务；如果康师傅从一开始就把工作效率提高12.5%，那么也可以提前4天完成任务．这批零件共有多少个？
<gadget id="calculator">4 * 9</gadget>
<output>36</output>

<gadget id="calculator">4 * 6</gadget>
<output>24</output>

<gadget id="calculator">36 - 24</gadget>
<output>12</output>

<gadget id="calculator">720 / 12</gadget>
<output>60</output>

<gadget id="calculator">60 * 36</gadget>
<output>2_160</output>

<result>2_160</result>