What is the minimum area of cardboard required to make a cuboid carton with a length of 5 cm, a width of 5 cm, and a height of 8 cm? If a, b, and h are used to represent length, width, and height, please summarize a calculation formula.
做一个长5厘米，宽5厘米，高8厘米的长方体的纸盒至少要面积是多少的硬纸板？如果分别用a、b、h表示长、宽、高，请你总结一个计算公式．
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