This is the answer to part A need help with B?

Denver is the correct answer what is the cost?

1=Yes, 0=No Boston Atlanta Houston Total sent Capacity Detroit 1 0 20000 0 20000 20000 0 Toledo 1 30000 0 0 30000 30000 0 Denver 0 0 0 0 0 40000 0 Kansas City 0 0 0 0 0 10000 0 St. Louis 1 0 0 20000 20000 30000 -10000 Total received 30000 20000 20000 Demand 30000 20000 20000 Plant \ DC Open or not? 1=Yes, 0=No Boston Atlanta Houston Detroit $175,000 $5 $2 $3 Toledo $300,000 $4 $3 $4 Denver $375,000 $9 $7 $5 Kansas City $500,000 $10 $4 $2 St. Louis - $8 $4 $3 Total cost 695000 Total cost = $695,000 What is the optimal set of plants to open? Detroit and Toledo (excluding St. Louis which is already existing) (b) Please post equation 12.1 to get the solution.