Which of the following situations would increase a buyer's bargaining power?

When a buyer’s purchase represents asignificant portion of a supplier’s revenue, it increases the buyer’s leverage. The supplier has a vested interest in maintaining the relationship and is more likely to make concessions to preserve the account.

“Buyer power increases when the buyer represents a large portion of the supplier's total sales. This dependency increases the buyer’s ability to influence terms.”

(L4M5 Commercial Negotiation, 2nd edition, Section 2.3 - Bargaining Power Analysis)