The TV factory planned to produce 540 machine tools in 20 days, but actually produced 144 in the first 4 days. According to this calculation, how many days can the task be completed in advance?
电视机厂计划20天生产机床540台，实际前4天就生产了144台，照这样算，可以提前几天完成任务？
<gadget id="calculator">144 / 4</gadget>
<output>36</output>

<gadget id="calculator">540 / 36</gadget>
<output>15</output>

<gadget id="calculator">20 - 15</gadget>
<output>5</output>

<result>5</result>