To determine the optimal product mix in Excel, you can use the Solver add-in program. By setting up a Solver model, you can maximize profitability while considering constraints such as limited resources and demand. The SUMPRODUCT function can help you efficiently compute resource usage and profit, and the Assume Linear Model option in Solver can optimize the solution. The article mentioned in the reference provides a detailed explanation and example of how to use Solver for determining the optimal product mix.