So let's make that into a little tile, this one into it that also has some depth to it. You could even, I could draw it multiple places. You could view it as a, break it up into these things that have a very small depth that we could call dx. And we know how to figure out what their volume is. What would be the volume of one of these things? Well, it would be the depth times the area, times the surface area of this cross section right over here. Let me do that in a different color.