原帖由 <i>springspsp</i> 于 2010-4-24 20:20 发表 <a href="http://www.romabbs.com/redirect.php?goto=findpost&pid=801723&ptid=25339" target="_blank"><img src="http://www.romabbs.com/images/common/back.gif" alt="" border="0"></a>
边际效用 lz是学经济的吧~ 第二十六个包子那岂不是负效用了~
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