A certain project can be completed by teams A and B in 2 and (2/9) days and needs to pay 1800 yuan; it can be completed by teams B and C in 3 and (1/13) days and needs to pay 1520 yuan; Team contracting can be completed in 2 and (2/3) days, and a payment of 1680 yuan is required. Under the condition of guaranteeing the completion within 7 days, which team should choose the least cost of contracting alone? How much is the minimum cost?
某项工程由甲乙两队承包2又(2/9)天可以完成，需支付1800元；由乙丙两队承包3又(1/13)天可以完成，需支付1520元；由丙甲两队承包2又(2/3)天可以完成，需支付1680元．在保证7天内完成的条件下，选择哪个队单独承包的费用最少？这个最少的费用是多少元？
<gadget id="calculator">20 / 9</gadget>
<output>20/9 = around 2.222222</output>

<gadget id="calculator">1_800 / (20/9)</gadget>
<output>810</output>

<gadget id="calculator">40 / 13</gadget>
<output>40/13 = around 3.076923</output>

<gadget id="calculator">1_520 / (40/13)</gadget>
<output>494</output>

<gadget id="calculator">8 / 3</gadget>
<output>8/3 = around 2.666667</output>

<gadget id="calculator">1_680 / (8/3)</gadget>
<output>630</output>

<gadget id="calculator">810 + 494 + 630</gadget>
<output>1_934</output>

<gadget id="calculator">1_934 / 2</gadget>
<output>967</output>

<gadget id="calculator">967 - 630</gadget>
<output>337</output>

<gadget id="calculator">337 * 5</gadget>
<output>1_685</output>

<result>1_685</result>