154. So, you mean here D is the cost.
170. 现在我觉得题目也许有误,因为第二个条件与题目有矛盾,不是么?
不过我同意你的观点,因为从(1)的确无法得到4时的百分数。
But I always puzzled by this kind of problems about "median". I used to draw an abscissa. What do you think about it? Should I always change "=< or =>" to "> or <"? Is there any different?
Thank you.作者: tongxun 时间: 2002-10-5 23:43