Question

Consider the alphabet X+{C,D,S,T,X,Z}
a) how many strings of length 17 over alphabet contain 4C's 2T's *X's and 3Z's?
b)How many of the above described strings have all 4C's before the 2 T's???

Answer 1

i get the first part should be
17!/4!2!8!3!

but i am unsure about the last part.... the only way i KNOW that the four C's come first is if there are four in the first four places or if the T's are in the last two.... HELP would be greatly appreciated