Teacher Wang went to the supermarket to buy milk for the kindergarten children. Each box of milk is 56 yuan, and each box contains 12 boxes. Now the supermarket is offering a promotional discount. Buy 1 box and get 2 boxes free. If 840 children in the kindergarten each give 1 box, Teacher Wang How much is the minimum payment?
王老师到超市为幼儿园的小朋友买牛奶，每箱牛奶56元，每箱装有12盒，现超市正促销优惠，买1箱送2盒，如果幼儿园840个小朋友每人发1盒，王老师至少需付多少钱？
<gadget id="calculator">12 + 2</gadget>
<output>14</output>

<gadget id="calculator">840 / 14</gadget>
<output>60</output>

<gadget id="calculator">60 * 56</gadget>
<output>3_360</output>

<result>3_360</result>