题目内容：
The assetsection of the January 1, 20X7, balance sheet of Petticoat Company includes amachine which was acquired on January 1, 20X3. The machine.s original cost was $500,000, and the estimated life wasdetermined to be 10 years. The estimatedresidual value was zero, and the straight-line method of depreciation waschosen. If operating income before depreciation is$90,000, the rate of return on average net book value for 20X7 is:A、14.55%
B、13.33%
C、16.00%
D、32.79%
参考答案：