Problem $2$

A job shop has four work centers: A$,$ B$,$ C$,$ and D that are currently located in a facility as in locations $1,2,3,$ and $4$ as shown:

$\backslash$table$[[A$ in $1B$ in $2C$ in $3]]$

The distance in meters between each pair of locations are as follows:

$\backslash$table$[[1,2,3,4],[1,40,80,70],[2,,40,30],[3-,,,70],[4-,,,]]$

The loads moved between each pair of work centers per week are as follows:

$\backslash$table$[[,A,B,C,D$