The P&Q problem was presented by Eliyahu M. Goldratt in his book "The Haystack Syndrome: Sifting Information Out of the Data Ocean, Croton-on-Hudson, NY: North River Press Inc., 1990. The idea is to find the best product mix with a maximum net profit by varying the numbers of product P and Q under given circumstances.
In co-operation with Wolfram Research, I have launched an interactive simulation of the PQ-Problem to find the maximum net profit by a user.
GoTo http://demonstrations.wolfram.com/ThePQProblem/
PERMANENT CITATION, Jürgen Kanz, "The P&Q Problem", http://demonstrations.wolfram.com/ThePQProblem/, Wolfram Demonstrations Project, Published: June 25, 2020
A mathematical solution can be easily found by Integer Linear Programming. The Mathematica notebook "The P&Q-Problem Solution with Mathematica" in standard Mathematica format and CDF format shows a pragmatic way how to solve this kind of problem.
A copy of the Mathematica notebook in PDF format is available for interested readers that do not have access to Mathematica software.
I have added a Jupyter-Notebook for the free Wolfram Engine, https://www.wolfram.com/engine/. Information about the Wolfram Language kernel for Jupyter notebooks is available here on Github: https://github.com/WolframResearch/WolframLanguageForJupyter