A window washer is cleaning the bookstore windows .
There is a better than even chance that a book store owner is cleaning bird poop of his shop 's window .
There is a better than even chance that a book store owner is cleaning bird poop of his shop 's window .
It is improbable that a book store owner is cleaning bird poop of his shop 's window .
A book store owner is cleaning bird poop of his shop 's window .