The carton factory processes a batch of cartons for tools. The length of the carton is 20 centimeters, and the width and height are both 5 centimeters. How many square centimeters of hard paper are needed to make such a carton?
纸盒厂加工一批装工具的纸盒，盒长20厘米，宽和高都是5厘米，做一只这样的纸盒至少需要硬纸多少平方厘米？
<gadget id="calculator">5 * 5 * 2</gadget>
<output>50</output>

<gadget id="calculator">5 * 20 * 4</gadget>
<output>400</output>

<gadget id="calculator">50 + 400</gadget>
<output>450</output>

<result>450</result>