The first two methods — upper and lower — are easy to understand.

前两个方法upper和lower很容易理解。

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Among of them the first two methods are the extension of the net-value method.

三者中的前两者是净利法的推广。

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Among of them the first two methods are the extension of the net-value method.

三者中的前两者是净利法的推广。

youdao