Now, for those of you who took Economics 115 or equivalent, what is the name of this line I've just drawn?

我来问一下学过经济学115的同学,这条曲线叫什么名字

耶鲁公开课 - 博弈论课程节选

Then a brass instrument enters and what is the name of this brass instrument?

然后一个铜管乐器出现了,那么这个铜管乐器是什么

耶鲁公开课 - 聆听音乐课程节选