project needs 30 days to be completed by engineering team A, and the daily project cost is (2/3) ten thousand yuan; it takes 40 days to be completed by engineering team B, and the daily project cost is (1/4) ten thousand yuan. In order to complete the project within 20 days, arrange teams A and B to participate in this project. If the number of working days of the two teams can be different, then the total cost of the two teams to complete this project is at least how many yuan.
一项工程，甲工程队做需30天完成，每天工程费用(2/3)万元；乙工程队做需40天完成，每天工程费用(1/4)万元．为了在20天内完成，安排甲、乙两队共同参与这项工程，如果两队工作的天数可以不一样，那么，两队共同完成这项工程的总费用至少需要多少万元．
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">30 / 40</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">(2/3) * (3/4)</gadget>
<output>1/2 = around 0.5</output>

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

<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/2) / (1/30)</gadget>
<output>15</output>

<gadget id="calculator">15 * (2/3)</gadget>
<output>10</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(2/3) * 30 * (1/4)</gadget>
<output>5</output>

<gadget id="calculator">10 + 5</gadget>
<output>15</output>

<result>15</result>