Exercise 6.16 (Sudoku). On a board of 9×9 fields the following values are given: (1, 5):5, (1, 9):2, (2, 4):6, (2, 9):9, (3, 2):1, (3, 3):8, (3, 4):4, (4, 2):2,

(4, 3):3, (4, 5):7, (5, 3):5, (5, 5):6, (5, 7):2, (6, 7):6, (6, 8):4, (7, 6):2, (7, 7):8,

(7, 8):5, (8, 1):9, (8, 6):1, (9, 1):7, and (9, 5):3.

1 Draw a sketch of this board with the given values.
2 Find a Boolean model for these problems. How many Boolean variables are needed?
3 Solve this example using XBOOLE.