Object-Oriented Design: Design a Credit Card System

Design a simplified credit card system (OOD). Propose the core classes/interfaces and describe the main workflows. Support at least: Card/account lifecycle (create, status Active/Frozen/Closed) Credit limit and available credit Transactions: charge (authorize/capture simplified) and refund Billing: generate periodic statements; payments that update balance/used credit Basic validations (status, insufficient credit, optional duplicate detection) Constraints: No real payment-network integration; in-memory storage is fine. Provide key method signatures (e.g., authorize/charge/refund/generateStatement/makePayment). Explain responsibilities and relationships. Cover: Class design (fields/methods) Sequence for a charge and for statement+payment One extensibility idea (multi-currency/installments/fraud detection).