A piece of rectangular iron sheet (thickness is not counted), the four corners are cut off to make a square with a side length of 2.8 decimeters, and welded into a rectangular iron sheet box, which can hold 546 liters of water. It is known that the length of this rectangular iron sheet is 21.2 decimeters. Find the rectangle The area of the iron sheet.
一块长方形铁皮(厚度不计)，四个角剪去边长为2.8分米的正方形，焊成一个长方体铁皮盒，可以盛水546升，已知这块长方形铁皮的长是21.2分米，求长方形铁皮的面积．
<gadget id="calculator">2.8 * 2</gadget>
<output>5.6</output>

<gadget id="calculator">21.2 - 5.6</gadget>
<output>15.6</output>

<gadget id="calculator">15.6 * 2.8</gadget>
<output>43.68</output>

<gadget id="calculator">546 / 43.68</gadget>
<output>12.5</output>

<gadget id="calculator">12.5 + 2.8 + 2.8</gadget>
<output>18.1</output>

<gadget id="calculator">21.2 * 18.1</gadget>
<output>383.72</output>

<result>383.72</result>