1.Four years ago a company purchased a $500,000 machine with an estimated useful life of 10 years. For accounting purposes, the machine is used to manufacture a particular product and has no alternative use or scrap value. The annual revenue generated from operating the machine is $650,000 and the annual cost of the factors of production , other than depreciation, employed to generate that revenue is $600,000. Should the company continue to operate the machine?

A.Yes
B.No, because operating costs are equal to operating revenues.
C.No, because the purchase price of the machine is a sunk cost .
D.No, because the opportunity cost of operating the machine is zero.

请问：

为什么答案选A，把折旧算进去的话，应该是持平的呀？
另外为什么说machine is a sunk cost?
请帮忙分析一下。

2.Using the following information, calculate the firm's economic profit.
Revenues 200,000
Cash Expenses 100,000
Economic depreciation 15,000
Accounting depreciation 20,000
Normal profit 30,000
Forgone interest 12,000

请问应该怎么计算？accounting depreciation是否应该扣除？

第一个题目不要考虑机器的折旧，因为 the machine is used to manufacture a particular product and has no alternative use or scrap value，所以机会成本为０

accounting depreciation我认为不应该扣除，要扣除的是Economic depreciation ，当然对Economic depreciation 的定义题目中表达的不是很清楚。