Explanation
A low CPI value (0.53) indicates that the project is over budget. This may be due to an inaccurate cost baseline, which means the initial budget estimation was not correct. This would not necessarily mean that cost control processes are ineffective, actual reported costs are inaccurate, or cost-related risks are effectively managed.

A stakeholder impact and influence analysis is a technique to identify the level of interest and power of each stakeholder, and to assess how they may affect or be affected by the project outcomes. It can help the risk manager to understand the stakeholder's perspective and expectations, and to communicate with them effectively. In this case, the risk manager should perform a stakeholder impact and influence analysis to understand why the major investor is about to drop their intention to continue executing the project, and to address their concerns and needs. A risk impact analysis, a risk reserve analysis, and a procurement analysis are not relevant to the stakeholder's decision, and would not help the risk manager to understand their rationale. References: PMI Risk Management Professional (PMI-RMP)® Exam Content Outline1, PMI Practice Standard for Project Risk Management2, Risk Management Professional (PMI-RMP)® Cert Guide3

Meeting with the traffic authority staff responsible for the new regulation allows the project manager and risk manager to understand the potential changes and their impact on the project. This will help them proactively address any potential issues and ensure the project complies with the new regulations.
According to the PMBOK Guide, 6th edition, Chapter 11: Project Risk Management1, the project manager and the risk manager should handle this situation by meeting with the traffic authority staff in charge of the new regulation. This is because:
* The new traffic regulation is an external risk that could affect the project objectives, such as scope, schedule, cost, quality, and customer satisfaction. External risks are those that arise from outside the project boundaries and are beyond the control of the project team. Examples of external risks include changes in government policies, regulations, laws, market conditions, environmental factors, etc.
* The project manager and the risk manager should proactively engage with the external stakeholders who have the power and influence to create or modify the external risks. By meeting with the traffic authority staff, they can establish a positive relationship, gain insights into the new regulation, and influence its development to align with the project needs. They can also obtain information on the probability and impact of the risk, as well as the potential response strategies.
* The other options are not effective in handling this situation because:
* Ensuring the project complies with the current traffic regulations and laws does not address the risk of the new regulation that could change the project requirements, scope, or deliverables. It also does not help the project team to prepare for the possible changes and mitigate their negative effects.
* Sending a letter to the traffic authority with the general project information does not establish a direct and timely communication channel with the external stakeholder. It also does not provide enough details or feedback to understand the nature and implications of the new regulation.
* Performing inquiries on the website of the traffic authority weekly does not allow the project team to influence the development of the new regulation or obtain reliable and updated information. It also does not enable the project team to build trust and rapport with the external stakeholder.
References:
* PMBOK Guide, 6th edition, Chapter 11: Project Risk Management1
* Risk Management Professional (PMI-RMP) Exam Cert Guide2