Each of these degradations represents an economic life period in a different service. 每一次降级均代表在不同服务岗位上的经济寿命期。
To do the calculation, you will have to prepare a spreadsheet table showing all costs after taxes over each investment's economic life. 为了完成计算，你将必须准备一张显示每种投资在其经济寿命期间的全部税后成本的电子表格。
