How many decision variables does the problem have?

The Transportation Problem:

Wheat is harvested in the Midwest and stored in grain elevators in three different cities, Kansas city,

Omaha and Des Moines. These grain elevators supply flour mills located in three cities, Chicago, St$.$

Louis and Cincinnati. Grain is shipped to the mills in railroad cars. Each car is capable of holding $1$ ton of

wheat. Solve a transportation problem based upon the following data:

Grain Elevator SUPPLY AVAILABLE

$1.$ Kansas city $150$

$2.$ Omaha $175$

$3.$ Des Moines $275$

Each mill has the following demand profile every month:

MILL DEMAND

Chicago $200$

St$.$ Louis $100$

Cincinnati $300$

The transportation cost per ton from each supply node to each demand node is given below:

Chicago St$.$ Louis Cincinnati

Kansas city $$6$ $$8$ $$10$

Omaha $71111$

Des Moines $451$