If the base of a cuboid is a square with side length 20 cm and height 40 cm, if its height is increased by 5 cm, how much will its surface area increase?
一个长方体底面是一个边长为20厘米的正方形，高为40厘米，如果把它的高增加5厘米，它的表面积会增加多少？
<gadget id="calculator">20 * 4 * 5</gadget>
<output>400</output>

<result>400</result>