7. A company has 16 machines in inventory at locations $A$ and $B$. Now, these machines need to be transported to locations 甲 and 乙, with 15 machines required at 甲 and 13 machines required at 乙. It is known that the transportation cost from $A$ to 甲 is 500 yuan per machine, and to 乙 is 400 yuan per machine; the transportation cost from $B$ to 甲 is 300 yuan per machine, and to 乙 is 600 yuan per machine. What transportation plan should be designed to minimize the total transportation cost?
7. Send 3 units from $A$ to location 甲, 13 units to location 乙; send 12 units from $B$ to location 甲, 0 units to location 乙, to minimize the total transportation cost, the minimum cost is 10300 (yuan).