Anna has 4 books. If she decide to arrange the 4 books in every possible combination and moved just one book every minute, how long would it taken by her ?	Choose the correct answer:
A) 22 minutes
B) 30 minutes
C) 15 minutes
D) 24 minutes
E) 35 minutes
Number of ways of arranging 4 books = 4 ! = 4 x 3 x 2 x 1 = 24.   So, total time taken = 24 minutes   Answer: 24 minutes
<result>D</result>
Anna has 4 books. If she decide to arrange the 4 books in every possible combination and moved just one book every minute, how long would it taken by her ?