I'm going through some past papers for an exam which has the production planning problem and formulating linear programming problems in it but I've come across a question that is an odd mix of both.
It gives a limit to weekly production, the demands for the next four weeks, the costs of backlogging and inventory storage (plus their limits) and the cost of production. The objective function you're seeking is for the optimal production plan (so I assume maximising profit) and it specifically states that you should not solve the problem.
It gives all the information you'd need to solve this as a production planning problem but I've never come across a combination of the two. How do I formulate this?
So far all I've worked out is that the decision variables are the four amounts produced which must be above zero and below the weekly production limit.
Any help greatly appreciated.
EDIT: I have typed out the whole question as best I can below
A factory can make at most $10$ units a week and there is demand forecast to be $8, 14, 11, 7$ for the next four weeks. $7$ units can be held in inventory at a cost of £10 a unit/week, orders for up to $3$ units can be backlogged at a cost of £15 a unit/week. There is currently no inventory and no orders backlogged and we want none at the end of the four weeks.
The cost of production is $0$ if $n=0$
$100$ if $0<n\leq6$
$130$ if $6<n\leq8$
$150$ if $9<n\leq10$