[solved] The bargaining leverage of suppliers is stronger when
suppliers provide an item that accounts for a sizable fraction of the costs of the industry's product.
there are no good substitutes for the items being furnished by the suppliers and when there are only a few "preferred" suppliers of a particular input.
industry members purchase in large quantities and thus are important customers of the suppliers.
the products of suppliers are weakly differentiated and the supplier industry is composed of more than five suppliers.
industry members are a threat to integrate backward into the business of suppliers and to self-manufacture their own requirements.