Bottom-up estimation is the most detailed and least risky method, especially in complex projects like international construction with localized legal constraints. It allows for the incorporation of precise data, including legal compliance costs, permitting, and regulatory timelines.

The PMBOK® Guide – Seventh Edition identifies bottom-up estimating as highly accurate because it breaks down the work into smaller packages and estimates each individually. This method is especially useful when local context is critical and legal factors may impact cost.

Option A (parametric estimation) assumes standard historical metrics, which may not be valid across jurisdictions.

Option B (top-down with contingencies) is higher risk and less precise.

Option C is vague and may miss crucial localized compliance costs.