Effective use of these methods to control technology depends on whether or not the goal of regulation is the optimal allocation of resources. When the object is optimal resource （45） allocation， that combination of legal methods should be used that most nearly yields the allocation that would exist if there were no external costs resulting from allocating resources through market activity. There are external costs， when （50） the price set by buyers and sellers of goods fails to include some costs to anyone， that result from the production and use of the goods. Such costs are internalized when buyers pay them.
Air pollution from motor vehicles imposes （55） external costs on all those exposes to it， in the form of soiling， materials damage， and disease， these externalities result from failure to place a price on air， thus making it a free good， common to all. Such externalities lead to nonopti（60） mal resource allocation， because the private net product and the social net product of market activity are not often identical. If all externalities were internalized， transactions would occur until bargaining could no longer improve the （65） situation， thus giving an optimal allocation of resources at a given time.英语作文
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