Using Vogel's Approximation method, determine the minimum optimal transportation cost.

Wheat is harvested in the Midwest of the USA and stored in grain elevators in four different cities—Evansville (A), Kansas City (B), Omaha (C), and Des Moines (D). These grain elevators supply four flour mills, located in Chicago (I), St. Louis (II), Grand Rapids (III), and Cincinnati (IV). Grain is shipped to the mills in railroad cars, each of which is capable of holding one ton of wheat. Each grain elevator is able to supply the following number of tons (i.e., railroad cars) of wheat to the mills on a monthly basis:

	I	II	III	IV	SUPPLY
A	4	6	8	13	50
B	13	11	10	8	70
C	14	4	10	13	30
D	9	11	13	8	50
DEMAND	25	35	120	20