The $80/20$ rule is $\_$a$.$ A concept where $80\%$ of suppliers provide $20\%$ of the materials.b$.$ A strategy where $80\%$ of the supply chain is automated and $20\%$ is manual.c$.$ An approach where $80\%$ of inventory is kept in storage and $20\%$ is kept on hand.d$.$ A rule that suggests $80\%$ of transportation costs come from $20\%$ of the routes.e$.$A small percentage of products generate the majority of demand and profit