A square iron sheet with a side length of 40 cm, cut off a square with a side length of 5 cm at each of the four corners, and then make a rectangular parallelepiped iron box without a lid. What is the surface area of this iron box in square centimeters?
一个边长为40厘米的正方形铁皮，四角各剪去一个边长5厘米的正方形，然后做成一个无盖的长方体铁盒，这个铁盒的表面积是多少平方厘米？
<gadget id="calculator">2 * 5</gadget>
<output>10</output>

<gadget id="calculator">40 - 10</gadget>
<output>30</output>

<gadget id="calculator">30 * 30</gadget>
<output>900</output>

<gadget id="calculator">30 * 5</gadget>
<output>150</output>

<gadget id="calculator">900 + 150 + 150</gadget>
<output>1_200</output>

<gadget id="calculator">1_200 * 2</gadget>
<output>2_400</output>

<gadget id="calculator">2_400 - 900</gadget>
<output>1_500</output>

<result>1_500</result>