In how many different ways can 4 physics, 2 math, and 4 chemistry books be arranged in a row so that all books of the same subject are together?  Choose the correct option
A) 5842	B) 6912	C) 7782	D) 8132	E) 9452
Let's think of each subject as a group so there are 3 groups.   The number of ways to arrange these 3 groups is 3!   Within each subject the books can be re-arranged.   So we need to multiply 3! by 4!*2!*4! which is 3!*4!*2!*4! = 6912   The answer is 6912.
<result>B</result>
In how many different ways can 4 physics, 2 math, and 4 chemistry books be arranged in a row so that all books of the same subject are together?