Using structured analysis, draw first a context diagram for a credit - card system described below. Then, go ahead and depict details of the functionality of the system. You are free to make assumptions as needed, but make sure that you have stated them clearly.

The credit - card system under consideration handles transactions for retail stores. For instance, a transaction might consist of buying a textbook from your favorite bookstore. Your data flow diagram(s) should include functions for retrieving and checking a credit - card record for a customer, approving and recording each transaction, and maintaining a log of transactions for each retail store. The system should maintain files of credit - card holders, current transactions, and accounts payable (approved transactions) for each store.