A large enterprise uses a single Shared VPC across 100 different projects. The finance team needs to implement a strict chargeback model to bill individual departments for their specific network egress costs and Compute Engine usage. What is the most reliable way to allocate these costs?

Use Network Tags on the VMs and filter the billing reports by tag.

Apply GCP resource labels (e.g., 'department:marketing') to all resources and export Cloud Billing data to BigQuery for analysis.

Create a separate billing account for each department and link their projects to it.

Use the Cloud Pricing Calculator at the end of each month to estimate what each department used.