考試會反覆打的機制：絕對優勢可以兩樣都有，比較優勢不能；專門化提高總產量；互惠貿易比率夾在兩國機會成本之間；運費高過總得益就不會貿易。Exam mechanisms: absolute advantage can hold for both goods, comparative advantage cannot; specialization raises world output; mutually beneficial TOT lies between the two opportunity costs; trade stops when transport cost exceeds total gain.