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) a Sold (AuctionID, BuyerUsername, DateSold) 1. Find usernames of the users who have a rating higher than 4.5. 2. Find a distinct list of usernames of the users who participate in an auction. Note that a user may participate in an auction as either a buyer or a seller. 3. Find a list of usernames of the sellers whose items have been sold. 4. Find a list of AuctionIDs for the auctions that have been expired. (Hint: An expired auction is the one whose item is not sold and EndTime