So it seems like we've met that because if you're differentiable over an interval, you're definitely continuous over that interval. I'm not saying that it's just a generally differentiable function f, I guess, over any interval. But the next part is to say, all right, that if that condition is met, then the slope of the secant line between four comma f of four and six comma f of six, that some, at least one point in between four and six, will have a derivative that is equal to the slope of the secant line. And so let's figure out what the slope of the secant line is between four comma f of four and six comma f of six. And if it's equal to five, then we could use the mean value theorem. If it's not equal to five, then the mean value theorem would not apply. And so let's do that.