应用题用图分析吉芬品的替代效应与收入效应，并进一步说明需求曲线的特征。

应用题某大学生只有6天时间应付期末考试。该生要靠数学、经济学、英语三门课。他的目标是要求得三门课尽可能高的成绩（或者说三门课尽可能高的平均成绩）。他每门课的成绩依赖于他分配在每门课上的复习时间。根据时间的安排，每门课成绩最佳估计分数如下：该生应如何让分配复习时间才能使总成绩最高？说明理由

应用题假定社会预付的产业资本是720c+180v=900，剩余价值率为100%，一年内生产的商品总价值为720c+180v+180m=1080 (假定不变资本的价值全部转移)，产业资本的利润率是多少？为了销售商品，流通领域内还必须垫支一定量的资本，假定由商业资本垫支100，那么平均利润率是多少？产业利润和商业利润各是多少？

应用题请简要说明长期平均成本LAC曲线呈U型特征的决定因素。

应用题某公司因业务发展需要，准备购入一套设备。现有甲、乙两个方案可供选择，其中甲方案需投资20万元，寿命期末无残值，每年销售收入为10万元，经营成本为3万元。乙方案需投资建设资金24万元，期初需投入流动资金3万元，寿命期末残值为4万元，每年销售收入为12万元，经营成本为4万元。两方案使用寿命均为5年，采用直线法计提折旧。假设所得税率为25%， 试求： （1）两个方案的现金流量图（5分）。 （2）如果折现率为10%，请用净现值法对两个方案作出取舍（10分）。

应用题在一个封闭经济社会中，已知消费需求为C＝80＋0.75Yd（Yd为可支配收入）,税收为T＝－20＋0.2Y,投资需求为I＝50＋0.1Y，政府支出G＝200，求经济均衡时的收入、消费、投资、税收。

应用题设某消费者效用函数为 ，消费者的收入为M，x, y两商品的价格为 ，求消费者对于x, y两商品的需求。

单选题In the USA, 85% of the population over the age if 21 approve of the death penalty. In the many states whcih still have the death penalty, some use the electric chair, which can take up to 20 minutes to kill, while others use gas or lethal injection. The first of these was the case of Ruth Ellis who was hanged for shooting her lover in what was generally regarded as a crime of passion. The second was hanged for murders which, it was later proved, had been committed by someone else. The pro-hanging lobby uses four main arguments to support its call for the reintroduction of capital punishment. First there is the deterrence theory, which argues that potential murderers would think twice before committing the act if they knew that they might die if they were caught. The armed bank robber might, likewise, go back to being unarmed. The other two arguments are more suspect. The idea of retribution demands that criminals should get what they deserve: if a murderer intentionally set out to commit a crime, he should accept the consequences. Retribution, which is just another word for revenge, is supported by the religious doctrine of an eye for an eye and a tooth for a tooth. The arguments against the death penalty are largely humanitarian. But there are also statistical reasons for opposing it: the deterrence figures do not add up. In Britain,1903 was the the record year for executions and yet in 1904 the number of murders actually rose. There was a similar occurrence in 1946 and 1947. If the deterrence theory were correct, the rate should have fallen. The other reasons to oppose the death penalty are largely a mather of individual conscience and belief. One is that murder is murder and that the state has no more right to take a lifer than the individual. The other is that Christianity advises forgiveness, not revenge.

单选题中国多所高校在多伦多、纽约、波士顿、旧金山召开了4场人才招聘会，针对出席招聘会的中国留学生做了问卷调查。调查显示：67%的人希望回国工作，33%的人会认真考虑回国的选择。可见，在美国工作对中国留学生已失去吸引力，人心思归已蔚然成风。 以下哪一项陈述准确指出了上述论证的缺陷?

单选题风险规避者的无差异曲线( )。

单选题设X 1 ，X 2 ，X 3 服从区间[0，2]上的均匀分布，则E(2X 1 -X 2 +3X 3 )=______．

单选题所得税的增加将引起充分就业的预算盈余( )。

单选题For years Internet merchants have poured millions of dollars into new technologies to make their sites easier to use. So why aren't online customers happier? Customer satisfaction levels have remained almost flat through the last several years. The problem, according to Larry Freed, chief executive of a consulting and research firm called ForeSee Results, is not so much that consumers have ignored the many improvements made in recent years. Rather, he said, they still expect more from Internet shopping than it has delivered. "If we walk into a local store, we don't expect that experience to be better than it was a couple years ago," Mr. Freed said. "But we expect sites to be better. The bar goes up every year. " In ForeSee's latest survey, released last month, just five e-commerce sites registered scores higher than 80 out of 100, and no site scored higher than 85. It was much the same story a year ago, when just five scored higher than 80, with no site surpassing 85. "Scores have inched up over time for the best e-commerce companies, but the overall numbers haven't moved drastically," Mr. Freed said. "At the same time though, if you don't do anything you see your scores drop steadily. " That dynamic has been a challenge for online merchants and investors, who a decade ago envisioned Internet stores as relatively inexpensive (and therefore extremely profitable) operations. Now some observers predict a future where online retailers will essentially adopt something like the QVC model, with sales staff pitching the site's merchandise with polished video presentations, produced in a high-tech television studio. QVC.com is evolving in that direction. The Web site, which sold more than $1 billion in merchandise in 2006, has for the last five years let visitors watch a live feed of the network's broadcast. But in recent months, QVC.com has also given visitors the chance to watch archives of entire shows, and in the coming months visitors will be able to find more video segments from recent shows, featuring individual products that remain in stock. Bob Myers, senior vice president of QVC.com, said the Web site's video salesmanship is especially effective when combined with detailed product information, customer reviews and multiple photographs. About eight months ago, for instance, a customer said that she could not determine the size of a handbag from the photographs on the site because she could not tell the height of the model who was holding it. Within two weeks the site tested and introduced a new system, showing the bags with women of three different heights. The results were immediate: women who saw the new photographs bought the bags at least 10 percent more frequently than those who had not. Still, Mr. Myers said, video is a critically important element to sales. "E-commerce started with television commerce," he said. "The sites who engage and entertain customers will be winning here in the near future. " Such a prospect is not necessarily daunting to other e-commerce executives. Gordon Magee, head of Internet marketing for Drs. Foster & Smith, based in a Rhinelander, Wis. , said a transition to video "will be seamless for us. " The company, Mr. Magee said, has in recent weeks discussed putting some of its product on video "so customers could see a 360-degree view they don't have to manipulate themselves. /

单选题设F 1 (x)，F 2 (x)为两个分布函数，其相应的概率密度f 1 (x)，f 2 (x)是连续函数．则必为概率密度的是______．

单选题若A，B均为n阶方阵，则正确的是______．