The Shamrock Transportation Company Has Four Terminals: A, B, C

The Shamrock Transportation Company has four terminals: A, B, C, and D. At the start of a particular day, there are 8, 8, 6, and 3 tractors available at those terminals, respectively. During the previous night, trailers were loaded at plants R, S, T, and U. The number of trailers at each plant is 2, 12, 5, and 6, respectively. The company dispatcher has determined the distances between each terminal and each plant, as follows. How many tractors should be dispatched from each terminal to each plant in order to minimize the total number of miles traveled?
$\begin{array}{|l|r|r|r|r|r|}\hline\text { COSTS } & \text { Dest. 1 } & \text { Dest. 2 } & \text { Dest 3 } & \text { Dest. } 4 & \text { Supply } \\\hline \text { Origin 1 } & 21 & 44 & 25 & 40 & 8 \\\hline\text { Origin 2 } & 42 & 24 & 45 & 22 & 8 \\\hline\text { Origin 3 } & 78 & 32 & 42 & 55 & 6 \\\hline\text { Origin 4 } & 44 & 42 & 32 & 30 & 3 \\\hline\text { Demand } & 2 & 12 & 5 & 6 & 25/25 \\\hline\end{array}$