$\backslash$table$[[$From$,$To$,$SUPPLY$],[1,2,3],[$A$,,$$$7,,$$$10,,$$$5,90],[$B$,,$$$12,,$$$9,,$$$4,50],[C,,$$$7,,$$$3,,$$$11,80],[D,,$$$9,,$$$2,,$$$7,60],[$DEMAND$,120,,110,,100,,]]$

a$.$ Set up the transportation tableau for this problem, determine the initial solution using northeast model, minimum cell cost model and VAM, and compute total cost.

b$.$ Solve previous VAM using MODI.

c$.$ Are there multiple optimal solutions? Explain. If there are alternative solutions, identify them.

d$.$ Formulate this problem as a linear programming model.