The project manager should communicate with the affected stakeholders first after realizing that the sign-off for the project scope baseline is delayed due to multiple changes and that the budget for this project is restricted by the project sponsor. The affected stakeholders are those who have an interest or influence on the project and may be impacted by any changes or delays. Communicating with them can help to explain the situation, assess the impact, seek feedback, and manage expectations.

Explanation
The project manager should use synchronous communication methods if they prefer to have immediate contact with team members. Synchronous communication is a type ofcommunication that occurs in real time and allows for faster response times and more interactive discussions. Examples of synchronous communication methods include phone calls, video conferences, instant messaging, and face-to-face meetings. Synchronous communication can help to build rapport, clarify doubts, and resolve issues quickly among team members.
Synchronous communication should be used when the project manager prefers to have immediate contact with team members. Synchronous communication allows for real-time interaction and feedback, enabling faster response times and more interactive discussions. References: CompTIA Project+ Study Guide Section 3.1.3

Identifying the root cause analysis. Identifying the root cause analysis is a quality assurance tool that can help to find and eliminate the underlying causes of quality problems or defects. Root cause analysis is a systematic process of asking why a problem occurred and tracing it back to its source. Root cause analysis can help to prevent recurrence of the same or similar problems, improve quality performance, and reduce costs and risks1
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Explanation
Identifying the root cause analysis. Identifying the root cause analysis is a quality assurance tool that can help to find and eliminate the underlying causes of quality problems or defects. Root cause analysis is a systematic process of asking why a problem occurred and tracing it back to its source. Root cause analysis can help to prevent recurrence of the same or similar problems, improve quality performance, and reduce costs and risks1
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Explanation
Regression testing is a type of testing that is done on an existing system to ensure that the previous functionality still works after a change has been made. Regression testing is a process of retesting or verifying that a software system or application still performs as expected after it has been modified or updated with new features, bug fixes, patches, etc. Regression testing can help to detect any errors or defects that may have been introduced by the change and ensure that no functionality has been broken or degraded.