It is known that 3 model workers and 6 ordinary workers can produce 420 parts in 8 hours. Now there are a batch of production tasks that need 6 model workers and 12 ordinary workers to produce for 14 hours to complete. If after working for 4 hours, 4 model employees and 8 ordinary employees come, how many hours can the task be completed in advance?
已知3名模范职工和6名普通职工8小时可以生产零件420个．现在有一批生产任务，需要6名模范职工和12名普通职工生产14小时才能完成．如果工作了4小时后，又来了4名模范职工和8名普通职工，可以提前几小时完成任务？
<gadget id="calculator">10 - 6</gadget>
<output>4</output>

<result>4</result>