Auction UC - Close Auction

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1. Close Auction
1.1 Brief Description
At the expiration of the end of auction timer, this use case closes out an auction. The end of auction timer is set when the Seller specifies a bidding time limit when the auction is created. See the Create Auction use case.
When an auction is closed, the current best bid for the item is accepted (the best bid becomes the purchase price for the item). The system notifies the Buyer and Seller that the auction has completed and provides each with the final purchase price for the item, as well as contact information for the other.
The Seller's credit card (credit card information is maintained with the auction and/or with the user account) is charged the transaction fee.