A duck walks into a pet store and asked the owner if he sold “duck-food” here. The owner said; “no, I don’t sell duck food here”. The next day the duck went back to the same pet store, and asked the owner again if he sold “duck-food” here. The owner became very angry and said; “if you ask me for “duck-food” one more time, I am going to nail your web feet to the floor!” The duck came back on the third day and asked the owner of the pet store; “do you sell any hammer and nails here?” The owner answered; “no, I don’t sell any hammer and nails here”. The duck then asked; “do you sell any “duck-food” here”?