According to the PMP Exam Study Guide, a subject matter expert (SME) is a person who has specialized knowledge or skills in a particular domain or area. A SME can provide valuable input and guidance on technical, functional, or business aspects of a project. In this scenario, the project manager should consult with a SME to see if the proposed change is acceptable, as it may affect the quality, performance, or functionality of the product or service. The SME can help the project manager to assess the impact of the change, evaluate the alternatives, and make an informed decision. The project manager should not accept, insist, or instruct the vendor without consulting with a SME, as this may lead to poor quality, customer dissatisfaction, or contractual issues. References:
* PMP Exam Study Guide, Chapter 9: Project Resource Management, Section 9.1: Plan Resource Management, p. 443
* PMP Exam Study Guide, Chapter 12: Project Procurement Management, Section 12.2: Conduct Procurements, p. 535-536
* PMP Exam Study Guide, Chapter 13: Project Stakeholder Management, Section 13.3: Manage Stakeholder Engagement, p. 573-574