I have a production programming exercise that I'm supposed to solve by using the Excel solver. However, I am not able to set an integer constraint on a certain cell that I need to be integer only.
I attached a minimal example to this post, the structure is as follows:
There are 6 products, each with quantities to make-to-order and to make-to-stock, the sum of those two and their respective contribution margin. The total contribution margin is calculated as the sumproduct of the total quantity of each product multiplied with its contribution margin.
Now for the solver, I want to maximize the total contribution margin, by changing the make-to-stock values for each product and the make-to-order values for some products (there are some more constraints which are not relevant to this problem).
Now I already set the solver to where the problem happens, as soon as I try to add an integer constraint to a make-to-stock cell, where the make-to-order cell above it is set to change, I get the error "Integer Constraint Cell Reference must include only Variable Cells.". I don't understand why, because the cell (F3 in this case) is marked as a variable cell. Is this a bug in Solver, or am I completely missing something?
Minimal example: Link