In how many ways can the letters of the word 'Director' be arranged so that the three vowels are never together ?

In how many ways can the letters of the word 'Director' be arranged so

1.	In how many ways can the letters of the word 'Director' be arranged so that the three vowels are never together ?
A.	1800
B.	18000
C.	16000
D.	1600
Answer» C. 16000