Mai and books
Mai has moved into a new house and now she is organising her library. She wants to put 8 books on one shelf (each book has unique name), also she has a very picky taste. She has red, blue, green and yellow books, and from each color there are two books . She dislikes when red book is next to a green one, and when blue book is next to a yellow one. Also, she would like to avoid same-coloured books being neighbouring . On how many ways can Mai organise her library?
Important: Combination ABCDEFGH and HGFEDCBA will be considered as one combination.
To sum up: