You've got this policy tool of interest rates but once it hits zero you're out of business.

你拥有利率这一政策工具,但是一旦利率达到零点，你便失业了。

耶鲁公开课 - 金融市场课程节选

So if you get the CD set, not only do you get a wonderful beginning library of classical music but in effect you get a lifetime service contract with it.

所以一旦你买了整套CD,你不仅可以拥有一个古典乐图书馆,而且还可以享受终身服务

耶鲁公开课 - 聆听音乐课程节选