问题如下：
Ted Ltd. recently purchased a manufactoring machine for $60,000, which is expected to generate annual cash inflow of $25,000 for six years. The firm will depreciate the machine over six years for accounting purpose. However, the tax authority estimates the machine's useful life of 5 years. Assume tax rate is 40%, and the machines has no salvage value. What is the taxable income of Ted Ltd. in year 1 if straight-line method is used?
选项：
A.$12,000.
B.$13,000.
C.$15,000.
解释：
B is correct.
The tax authority estimates the machine's useful life of 5 years. Therefore annual depreciation expense=($60,000-0)/5=$12,000.
Taxable income in year 1 =$25,000-12,000=$13,000.
为什么这题用tax authority估计的年份5年，而另一个一样的题目用6年？
