In the Kraljic matrix, a product with high business impact and low supply market complexity is categorized as a leverage item. Leverage items have a significant impact on the business and are typically sourced from multiple suppliers, allowing the buyer to leverage their purchasing power to obtain favorable terms and conditions.
References
* Purchasing Must Become Supply Management by Peter Kraljic, Harvard Business Review
* Supply Chain Management: Strategy, Planning, and Operation by Sunil Chopra and Peter Meindl

In this scenario, the supply manager signed a contract exceeding their documented authority limit, but verbally assured the supplier of an increased signing limit. The key issue is the concept of apparent authority.
* Successful, as the supplier should have respected the written signing policy: This disregards the principle of apparent authority.
* Unsuccessful, because the supply manager's verbal statement represents a binding agreement:
Verbal statements alone may not constitute a binding agreement without supporting apparent authority.
* Unsuccessful, as the supply manager's status and statement constitute apparent authority:
Apparent authority exists when a third party reasonably believes that an individual has the authority to act on behalf of the organization. The supply manager's role and assurances create a reasonable perception of authority.
* Successful, provided the disavowal occurs within three business days of contract signing: No standard provision supports this within the given context.
Therefore, the attempt to disavow the contract will likely be unsuccessful, as the supply manager's status and statement constitute apparent authority.
References:
* Contract law principles on actual and apparent authority.
* Case studies on organizational liability for employees' actions.