Let's imagine an open interval. And sometimes if we want to be particular, we could make this is the closed interval right over here, brackets. And if we want to do an open interval right over here, that's a, that's b. And let's just pick a very simple function. Let's say a function like this. So right over here, if a were in our interval, it looks like we hit our minimum value at a. f of a would have been our minimum value. And f of b looks like it would have been our maximum value.