Trejo estimates that it costs $$1\mathrm{.}50$ per month for each unit of this appliance carried

in inventory at the end of each month. Currently, Trejo has $120$ units in inventory on

hand for this product. To maintain a level workforce, the company wants to produce

at least $400$ units per month. They also want to maintain a safety stock of at least

$50$ units per month. Trejo wants to determine how many of each appliance to

manufacture during each of the next $4$ months to meet the expected demand at the

lowest possible total cost.

a$.$ Draw a network flow model for this problem.

b$.$ Create a spreadsheet model for this problem and solve it using Solver.

c$.$ What is the optimal solution?

d$.$ How much money could Trejo save if the company were willing to drop the

restriction about producing at least $400$ units per month?