存在比较优势时！从互换中得到的好处是这样计算的！
A国电脑100台/小时  汽车10辆/小时
B国电脑300台/小时  汽车20辆/小时
对所有的数字进行一个处理，每个国家都除以各自一小时生产的电脑数，后取百分数！如下
A国为100% ， 10%
B国为100% ， 6.67%
可以很轻易的看出A国在生产汽车上有比较优势，B国在生产电脑上有比较优势！
由于通过了各自的比较优势来贸易互换，双方的总“产品交换率”可以提高3.33%！
因为（B国的100%+A国的10%）-（A国的100%+B国的6.67%）= 3.33%
为简便起见！我们假设两国平分提高的率！各得1.67%
那么A国在电脑生产方面的生产率可提高1.67%，最终变为101.67%。同样B国在汽车生产率上也提高了1.67%，变为8.34%。
最终两国的数据就变成了如下形式：
A国为101.67%，10%
B国为100%，   8.34%
通过和原来的数据相比较！就可以很明显的发现！透过交换后两国的情况都变好了！

我的解释就是这样！希望你能懂！

[此贴子已经被作者于2008-7-2 0:17:52编辑过]

绝对优势和比较优势是可以同时共存的！二者并不会产生什么冲突！

[此贴子已经被作者于2008-7-2 0:05:20编辑过]

Sorry. I don't know how to explain it in Chinese.

The textbook is right.

Let's assume the trading rate is pc:car = 12:1; both A and B spend half time to produce car and pc, therefore, A has 50 PCs and 5 Cars, B has 150 PCs and 10 Cars.
B would like to trade pc with car, because his bottom line is 15 pc to 1 car; while A would like to trade car with pc, as his bottom line is 1 car to 10 pc.

After trading: assume A gives up 4 cars.
A gets PC: 50 + 12*4 = 98, with one Car left. It costs A: 98/50*.5 + 1/5*.5=10.8 hours without trading.
B gets PC: 150 - 12*4 = 102, Car: 10 + 4 = 14. It costs B: 102/50*0.5 + 14/10*.5 = 1.04 hours without trading.

Therefore, both A and B can consume outside the PPF (production probability frontier). I am sure you will get it when you finish your study of microeconomics and macroeconomics.

Note: those calculation is just used to prove the theory is right, not the exact answer you can put on the paper when you take test or exam.

谢谢几位，还有那为外籍朋友。