XYZ firm operates factories in three towns (A, B, and C), which distribute to three retail stores (X, Y, and Z). The following table summarizes factory maximum supplies, stores' demands, and unit shipping costs. What is the optimal solution that minimizes costs?

X Y Z Supply

A 12 7 5 100

B 17 13 10 100

C 2 2 18 100

Demand 50 80 70