Room: Room # of Guests. For example, if there are two guests with the last name of West staying in the Coolidge room, the guest ID would be "West Room: Coolidge 2" without the quotation marks. Use the CONCAT (or CONCATENATE) function. Reference the Guest's Last Name, Room, and # of Guests in your function. Pay close attention to the spaces in the Guest ID. Copy and paste the function down the column to create the "Guest ID" for the other transactions.