Class 5 and Class 1 are going to turn a cuboid paper box into a love box for donations to Hope Primary School. When pasting the red paper, four pieces of rectangular red paper with a length of 50 cm and a width of 40 cm were used around it. What is the surface area of this paper box?
五1班同学准备把一个长方体纸盒改成给希望小学捐款的爱心箱．贴红纸时，四周正好用了4张长为50厘米、宽为40厘米的长方形红纸，这个纸盒的表面积是多少？
<gadget id="calculator">40 / 100_000</gadget>
<output>1/2_500 = around 0.0004</output>

<gadget id="calculator">50 * 50 * (1/2_500)</gadget>
<output>1</output>

<result>1</result>