一道大一的西方经济学问题，求大家帮帮忙！！！谢谢！！关于比较优势和机会成本！

Question

Gary and Diane must prepare a presentation for their marketing class. As part of their presentation, they must do a series of calculations and prepare 50 PowerPoint slides. It would take Gary 10 hours to do the required calculation and 10 hours to prepare the slides. It would take Diane 12 hours to do the calculations and 20 hours to prepare the slides.
问题：If Diane and Gary have the same opportunity cost of $5 per hour, is there a better solution than for each to specialize in calculating or preparing slides?
答案：If Diane specializes in calculating, her opportunity cost will be $60; hence, Diane would be better off if she paid Gary any amount less than $60 to do the calculating. Since Gary’s opportunity cost of doing the calculations is only $50, he would be better off if Diane paid him between $50 and $60 dollars to do the calculations. In this case, the total time spent on the project would be 20 hours.（看不懂！！为什么gary有两个比较优势？？）

Answer 1

比较优势比较的机会成本，不可能同时具有比较优势的，除非机会成本相等，因为一种机会成本是另一种机会成本的倒数。D不是在两面都有比较优势，那是绝对优势。机会成本越小的话，越有比较优势。
举个简答例子：
中国生产一台电脑机会成本20张桌子，美国的是10张桌子，美国的机会成本小，则美国生产电脑具有比较优势。那么美国生产电脑，中国生产桌子。
题中D在计算有比较优势，而G在做幻灯片有比较优势。需要把时间换算做工作量。