After completing development and internal testing phases, the next step is to conduct User Acceptance Testing (UAT). UAT is performed by the end-users to ensure the system meets their requirements and is ready for deployment.
According to the CompTIA Project+ PK0-005 exam objectives, under Domain 2.3: Explain the importance of quality management and testing in project management, UAT is a critical phase to validate that the product meets the business needs and requirements.

The project manager should validate against the scope statement and ask for sign-off after a system was
implemented and testing was successfully completed. The scope statement is a document that defines and
documents the project scope, objectives, deliverables, requirements, assumptions, and constraints. The scope
statement can help to establish a common understanding and agreement between the project manager and the
stakeholders on what the project aims to achieve and deliver. Validating against the scope statement means
checking whether the project deliverables meet the agreed-upon scope criteria and quality standards. Asking
for sign-off means requesting formal acceptance and approval of the project deliverables from the
stakeholders.

By negotiating a middle ground, the PM used compromise as a conflict resolution technique. Force and avoid do not build consensus, while smoothing minimizes issues but does not resolve them. Compromise achieves agreement acceptable to both sides.
Reference: CompTIA Project+ PK0-005 - Conflict Resolution; CompTIA Cloud+ CV0-004 Governance, Risk & Compliance domain.

The project manager can use the burn up chart to analyze the current status of the project based on its scope (value delivered), budget (cost), and schedule (time). A burn up chart is a graphical tool that shows how much work has been completed (burned up) versus how much work remains (scope) over time. It also shows how much budget has been spent (burned up) versus how much budget remains (budget) over time. A burn up chart can help to monitor and control the project progress and performance and identify any variances or deviations from the plan. The chart given shows that both scope and budget lines are above their respective target lines at any given time point. This means that less work has been completed than planned (scope variance) and more money has been spent than planned (budget variance) at any given time point. Therefore, the project is behind schedule and over budget.

The RACI (Responsible, Accountable, Consulted, Informed) matrix is used to document which resources are responsible for which tasks. The RACI matrix is a tool that helps to clarify roles and responsibilities on a project. It assigns a level of responsibility to each resource involved in the project. References: CompTIA Project+ Study Guide Section 3.4.
The project manager should use a RACI matrix to document which resources are responsible for which tasks.
A RACI matrix is a type of responsibility assignment matrix (RAM) that plots the roles and responsibilities of resources on a project team. RACI stands for Responsible, Accountable, Consulted, and Informed. A RACI matrix can help to clarify who does what on a project, avoid confusion and duplication of work, and improve communication and collaboration among team members.