How to solve set covering problem $,$ where the objective is to reduce the number of existing warehouses within the consission areas taking in consediration thraa factors : distance $,$ trasportation cost and demand $?$ and please provide numerical example $?$but how to apply it provide step by step example to understand please $,$ can you explain by set covering objective function and constrains $?$ addition is there any study where its consedring in modeling set covering problem three factors cost $,$distance and demand $?$and how you will formulate that with demand