I would create the billing system utilizing a three-tier architecture, comprising a client tier, a business tier, and a data tier. The system would include both a front-end and a back-end. Front-end : This would serve as the interface for office staff to enter patient information, doctor consultation hours, costs, and other relevant details. Back-end : This component would be responsible for processing tasks. It would manage patient data, schedule appointments, calculate invoices, handle insurance claims, and ensure data synchronization between the two locations for consistency. The system should ideally be cloud-based and provide secure access, fully compliant with HIPAA regulations. Features should include instant invoice generation, management of patient records, capabilities for insurance processing, appointment scheduling, and notifications. To ensure data consistency and real-time updates between the two locations, we will implement a central database system. The recommended tools include ASP.NET for the front-end, C# for business logic, and SQL Server for the database, as they are designed for enterprise-level applications and come with robust built-in security features.