The question of plant size assumes economic significance in any operation where the capital cost of the plant represents , in the form of depreciation, maintenance, etc., a substantial factor in the cost of the finished product. This situation is almost universally encountered in petroleum refining and petroleum chemical manufacture, but is slightly less common in some sections of the traditional chemical industry, where raw material costs may be of overwhelming importance. The economic importance of determining the most suitable plant capacity derives from the fact that the cost of building a plant is not proportional, in a simple sense, to the capacity (in practice, it is frequently assumed that the capital cost of plant will vary in proportion to the capacity taken to the power 0.6). The net effect of this, expressed simply, is that the cost building a plant of double capacity will not require double the cost. So long as the plant can be operated at its maximum capacity, it is clear that there is an economic incentive to design it on the largest possible scale. At the lower end of the capacity scale, the effect of depreciation increases by leaps and bounds. In a given set of condition, therefore, which will reflect the facilities operated by competitive companies, it is important to ensure that any project envisaged includes production facilities of not less than “minimum economic size”. 各位英语高手帮忙翻一下啊！！！