Q: 3 (IAS/2008)

In how many different ways can four books A, B, C and D be arranged one above another in a vertical order such that the books A and B are never in continuous position?
question_subject: 
Logic/Reasoning
question_year: 
2008
question_exam: 
IAS
question_sub_subject: 
Reasoning
question_topic: 
Analytical
stats: 
0,64,176,24,96,56,64