The AVC curve is U-shaped, declining at first due to efficiency, but eventually increasing due to dim inishing returns. The AFC curve decreases as output increases, and eventually flattens out. The ATC is U-shape because it is the sum of the decreasing-to-flat AFC curve plus the U-shaped AVC curve. ATC = AFC+AVC. 老师，这道题目的知识点，在cross elasticity这节课里面没有哦。请问在哪节课出现的

"Note that if the economy is operating at potential GDP (LRAS) when the monetary.." 这个LRAS是啥？

文中提到“To evaluate P&C insurance companies, Johansson tells Smith that she places emphasis on the efficiency of spending on obtaining new premiums.” 根据这点，似乎这道题选择underwriting expense ratio更合适。

为什么AD的这个向下倾斜的图，横坐标轴上不直接写AD，而是写GDP？

老师，div和FCFE之间的关系什么，FCFE不是股东了以自由支配的现金流吗？和股利有什么关系呢

这两条公式是不是一样？ 如果是一样，为何有两种写法？

The price of a good falls from $15 to $13. Given this decline in price, the quantity demanded of the good rises from 100 units to 120 units. The own-price elasticity of demand for the good is closest to: 老师，这道题目，分母为啥不是（120+100）/2，还有（15+13）/2 呢

non-recurring activities是啥意思，包含了一些什么

红线部分的例子不太理解，能否详细解释一下，多谢

箱线图的定义是什么，为什么就是绿色部分，题目中问的是四分位数，但是绿色图片只有三个数，这里怎么理解四分位数呢