A weekly electricity company has to carry out preventive maintenance on three plants. The time required for the maintenance of each plant cannot last more than one day. The electricity company works with three auxiliary service companies to which it must assign maintenance, which depending on their degree of specialization varies the cost of reviewing the plants. The cost is reflected in the attached table What should be the assignment of the auxiliary company so that the cost is the minimum? Central Central Central 1 2 3 Business 10 9 5 A Business 9 8 3 B Business 6 4 7