A key stakeholder requests a significant feature addition during the execution phase of a predictive project. The change would add substantial business value but would impact the timeline by 6 weeks and increase the budget by 15%. What should the project manager do FIRST?

Implement the change immediately since it adds substantial business value

Reject the change to protect the project baseline and maintain schedule commitments

Assess the full impact on scope, schedule, cost, and quality, then submit to the change control board

Negotiate with the stakeholder to defer the change to a future project phase