Colored 3×3 cube

3、A large can of red paint fell on this 3×3 cube, and all its surfaces, including its bottom, got covered with red paint.

1) The number of unit cubes have only one face painted red is 6 which equals to the faces of a cube.
2) The number of unit cubes have only two faces painted red is 12 which equals to the edges of a cube.
3）The number of unit cubes have only three faces painted red is 8 which equals to the vertexes of a cube.
4) The number of unit cubes have no face painted red is 1 which is the center of the larger cube.