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