On a shelf are placed six volumes side-by-side labelled A, B, C, D, E and F.
B, C, E, F have green covers while others have yellow covers.
A, D, B are new volumes while the rest are old volumes.
A, C, B are law reports while the rest are medical extracts. Which two volumes are old medical extracts and have green covers ? 

Answer: D. E, F
  Green Cover Yellow Cover New  Volume Old Volume Law Reports Medical Extracts
A   X X   X  
B X   X   X  
C X     X X  
D   X X     X
E X     X   X
F X     X   X

 Clearly, E and F are old volumes which have green covers and are medical extracts.