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 committed timeline

Conduct a comprehensive impact assessment on scope, schedule, cost, quality, and risk, then submit to change control board

Negotiate with the stakeholder to implement a reduced version of the feature