Six toy factories make dolls. Completed (1/2) of the second quarter plan in April, completed (3/7) of the second quarter plan in May, completed 450 in June, and the result exceeded the plan (1/4). How many plans do you need to make?
六玩具厂做玩具娃娃．四月份完成了第二季度计划的(1/2)，五月份完成了第二季度计划的(3/7)，六月份完成了450个，结果超出了计划的(1/4)．计划需要做多少个？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">(1/4) - (1/2) - (3/7)</gadget>
<output>-19/28 = around -0.678571</output>

<gadget id="calculator">1 + (-19/28)</gadget>
<output>9/28 = around 0.321429</output>

<gadget id="calculator">450 / (9/28)</gadget>
<output>1_400</output>

<result>1_400</result>