Seven different books (A, B, C, D,E,F and G) are to be arranged on a shelf. Books A , B and C are to be arranged first and second starting from the right of the shelf. The number of different orders in which books D,E, F and G may be arranged is  Choose the correct choice.
A) 4!
B) 15!
C) 16!
D) 28!
E) 42!
Solution   Since books A,B and C are arranged first and second, only books D, E,F and G will change order. Therefore it an arrangement problem involving 4 items and the number of different order is given by   4!   4!nswer 4!
<result>A</result>
Seven different books (A, B, C, D,E,F and G) are to be arranged on a shelf. Books A , B and C are to be arranged first and second starting from the right of the shelf. The number of different orders in which books D,E, F and G may be arranged is