We have designed an eBay-like on-line auction database. Please use relational algebra to write queries in order to obtain the requested information. (Note: Every auction listed in the system, sold, expired, or ongoing, is listed in Auction table. Auctions, whose items have been sold out, are also listed in Sold table.)

Item (ItemID, ItemName, Description) User (Username, Email, Rating)

Auction (AuctionID, ItemID, SellerUsername, Price, StartTime, EndTime)

Sold (AuctionID, BuyerUsername, DateSold)

Find the ItemName of the highest priced item, along with the Username of the corresponding user selling the item. Note that there may be more than one item at the highest price, in which case, you must return the information for all items.