Third, one nation can sell some items at a lower cost than other countries and will also buy what it needs from those countries that have comparative advantage in the desired items.

第三，一个国家能够比别的国家以较低成本销售某些产品，而且还从对有关产品具有比较优势的国家购买所需产品。

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Hospitals can buy replacements at just over cost and at a discount to give or sell to new parents.

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