The perimeter of some rectangles is 200 centimeters, and their length and width are both greater than 20 meters. What is the maximum difference between the areas of the two rectangles?
一些矩形的周长都是200厘米，它们的长和宽都是大于20的整理米数．其中两个矩形面积之差最大是多少．
<gadget id="calculator">51 * 49</gadget>
<output>2_499</output>

<gadget id="calculator">100 - 21</gadget>
<output>79</output>

<gadget id="calculator">79 * 21</gadget>
<output>1_659</output>

<gadget id="calculator">2_499 - 1_659</gadget>
<output>840</output>

<result>840</result>