$1)$ In the textbook$/$ class example $($example $14\mathrm{.}2),$ we saw how to recognize trade$-$offs and include different inventory costs to make transportation mode choice decisions. Based on the Excel model and concepts, answer the following questions:

a$)$ Why is Golden Freightways new proposal not attractive, even though they provide the lowest rate $($$$3/$ cwt marginal$)$ among all the proposals.

b$)$ Show how the annual demand $($starting at $50,000$ units and increasing in increments of $10,000$ units up to a maximum of $200,000$ units$)$ impacts the total cost under the different transportation alternatives. Depict the same using a scatter plot.

$(12\mathrm{.}5$ points$)$

$2)$ In the textbook$/$ class example $($example $14\mathrm{.}4),$ we built an Excel decision model to capture the trade$-$off between transportation cost and responsiveness. Based on the Excel model and concepts, answer the following questions:

a$)$ Explain what is being depicted in the model.

b$)$ Using the Excel model, guide the decision maker as to how they can make the best decision as to whether they should aggregate shipments to customers and what the best aggregation option is$?$