I sell antiques and collectibles by renting booths in several antique shops in my tri-state area. I was wondering if any could give me any advice on how to do a profit & loss statement when I am not sure what the cost of the items I have sold? You see, in a few of my booths I have over 50,000 old postcards that when they are purchased the mall just records the sale as the quantity of postcards sold and the amount. There is no way for me to know which ones sold so I have no idea what I paid for them. Any ideas??