Companies A, B, and C Supply Components to Three Plants

Multiple Choice

Companies A, B, and C supply components to three plants (F, G, and H) via two crossdocking facilities (D and E) . It costs $4 to ship from D regardless of final destination and $3 to ship to E regardless of supplier. Shipping to D from A, B, and C costs $3, $4, and $5, respectively, and shipping from E to F, G, and H costs $10, $9, and $8, respectively. Suppliers A, B, and C can provide 200, 300 and 500 units respectively and plants F, G, and H need 350, 450, and 200 units respectively. Crossdock facilities D and E can handle 600 and 700 units, respectively. Logistics Manager, Aretha Franklin, had previously used "Chain of Fools" as her supply chain consulting company, but now turns to you for some solid advice.
-How many decision variables are in this problem?

A) 8
B) 9
C) 10
D) 12