Binky Rules: A Marc Brown Arthur Chapter Book 24 (Arthur Chapter Books)

Someone has been writing "Binky Rules" all over school property. The principal gets Arthur's friend, Binky, to clean up the mess, but Binky denies he's the one who did it. Super sleuths Buster and Fern try to solve the mystery. The only problem is they can't seem to agree on anything. Will they be able to discover who's been writing the graffiti before Binky really gets into to trouble?