For the initial layout given below, list all possible pairwise exchanges that would be considered by CRAFT. Assume department $B$ is fixed in its location. Use only one iteration of pair$-$wise exchange method $($such as exchanging A with C$)$ to develop a better layout from the initial layout and the material flow matrix $($F$)$ given below. Calculate the distance matrix $($D$)$ first $($the flow cost is $c_{ij}=1$ TL per unit per meter$).$

Initial Layout:

$\backslash$table$[[A,B,C,D,],[A,-,10,5,10],[B,-,-,20,15],[C,-,-,-,30],[D,-,-,-,-]]$

$\backslash$table$[[,$A$,$B$,$C$,$D$],[\frac{?}{\text{b}\text{a}\text{r}}(A),-,10,20,10],[$B$,-,-,$cdots,dots.$],[D,,-,-,]]$

b$)$ List all possible pairwise exchanges by CRAFT: $q,$

$q,$

$q,$

$q,$