PRACTICAL CONSTRAINTS: A TUTORIAL ON MODELLING WITH CONSTRAINTS ROMAN BART�K http://kti.mff.cuni.cz/~bartak/NASSLLI2003/files/paper4.pdf
A factory has four workers W1, W2, W3, and W4, and four products P1, P2, P3, and P4. The profit made by worker Wi working on product Pj is given by the following table. Assign workers to products so that each worker is assigned to one product and each product is assigned to one worker.
P1 P2 P3 P4
W1 7 1 3 4
W2 8 2 5 1
W3 4 3 7 2
W4 3 1 6 3