So we want to go from seven to four. Now, you might be tempted to say, okay, well, look, the area between f of x and x is two, so maybe this thing is two. But the key realization is this area only applies when you have the lower bound as the lower bound and the higher value as the higher bound. So the integral from four to seven of f of x dx, this thing, this thing is equal to two. This thing is depicting that area right over there. So what about this, where we've switched it? Instead of going from four to seven, we're going from seven to four.