$4.[20$pts$]$ Let us revisit the last question of Homework $2,$ where you created an optimization for Emirates Skycargo.

After conversations with Skycargo executives, you learn that that each storage area can be used for a single broker; in other words, no storage area can hold shipments from more than one broker. This is in addition to the various restrictions that were already mentioned in the original homework question.

$($a$).[10$pts$]$ Show how you would adjust the original formulation you obtained in homework $2$ and incorporate this complication. Clearly specify any changes and$/$or additions to the decision variables, objective function, and constraints.

$($b$).[10$pts$]$ Update the spreadsheet model for this problem to account for the formulation changes, and solve the resulting problem using Solver.