In situations with conflicting departmental priorities, the project manager should prioritize requirements based on a benefit-cost ratio analysis. This method ensures an impartial and quantitative approach to decision-making. By evaluating the potential benefits against the costs for each requirement, the project manager can objectively determine which requirements will deliver the greatest value to the organization. This approach aligns with best practices in project management and business analysis, which advocate for prioritizing requirements that maximize business value and stakeholder satisfaction123.