How many boxes are there between Box D and Box G?

Study the following information carefully and answer the question given below: Seven boxes namely A, Z, B, D, E, F and G are placed one above the other in the rack but not necessarily in the same order. The lowermost rack is numbered as one and above is two and so on. Box Z is placed immediately below Box E. Only one box is placed between the Box G and Box
D. Box E is placed in even numbered rack above the rack three. Box F is placed immediately above Box
D. Box B is not placed above Box
A. Neither Box A nor Box B is placed in lowermost rack. Only three boxes are placed between Box Z and Box G.