That's our f of x. And then we have minus f of three, which is nine. So it's six x minus 18. Six x minus 18. Well, that's the same thing as six times x minus three. And as we approach from the right, well, that's just going to be equal to six. So it looks like our derivative exists there, and it is equal to the limit as x approaches three of all of this business is equal to six, because the limit as we approach from the left and the right is also equal to six.