7. Most computers display images as a raster of points called pixels that can be addressed by their coordinates. These coordinates are ordered pairs and hence elements of a Cartesian product. We represent an image by coloring in the points that correspond to elements of a subset of a Cartesian product in the raster that represents the Cartesian product. Consider the raster below.
5
(1,5)
(2,5)
4
(1,4)
(3,4)
(4,5)
(5,5)
3
(2,3)
(4,3)
(5,4)
2
(1,2)
(2,2)
(4,2)
(5,2)
1
(1,1)
(2,1)
(4,1)
(5,1)
1
2
3
4
5
What is the subset of (1, 2, 3, 4, 5) \times (1, 2, 3, 4, 5) represented by the black pixels in the raster above?
