On a shelf the blue book is to the right of the red book, the yellow book is in one end, the black book is just before the white and the green is between blue and white. What is the order of the green book from left to right?
e. The problem has no logical solution
Another problem that seems to have more than one solution. I believe the problem lies in the placement of the yellow book, since we may have:
yellow | red | black | white | green | blue (5th) or
red | black | white | green | blue | yellow (4th)