toy factory needs to produce 4,000 toys. The first month is completed (1/4), the second month is completed (2/5), and the third month only needs to make a few to complete the task?
某玩具厂要生产4000个玩具，第一个月完成了(1/4)，第二个月完成了(2/5)，第三个月只要做几个就可以完成任务？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (1/4) - (2/5)</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">4_000 * (7/20)</gadget>
<output>1_400</output>

<result>1_400</result>