Please help me with this practice question. This will be the basis for study material and I need to understand how this process works Thanks!

Below I have attached a practice problem for reference:

Kingston Widgets (KW) anticipates the following demand for the next 6 months.

Month 1 2 3 4 5 6

Demand 250 350 450 350 550 250

Begining Month 1, KW has 100 widgets already.Each month KW can produce in its plant any # of widgets, at a fixed cost of $6000 per month (for operating the plant), and a unit production cost of $30 per widget. One month (any one) must be set aside for maintenance work, so the KW plant is available for production only during the remaining 5 months.KW could also buy widgets from another manufacturer at a cost of $70 per widget. Orders are placed at the beginning of the month and delivery is immediate. Each order must be for at least 120 widgets. No more than a total of 4 orders can be made.End of each month, a holding cost of $15 is charges to each widget in stock. Storage capacity is limited to at most 160 widgets in any month.

Decision Variables (including non binary ones)

Objective Function

Constraints (include binary and non negativity

Run solver on excel