combinatorics - Arranging letters

Using the letters $A,C,E,F,I,H,O,P,S,$ and $T$ (with no repetition),how many $4$ unique letter grouping can be created that:

a) Start with $A,C,E$ or end with $C,E,S,T$ ?

my approach is: $3$ choices for the first letter then 4 choices for the last letter,now i have used only $2$ letters, so we are left with 8 letters.

$(3)(8)(7)(4)= 672$

However, it does not match the answer that I have.Most likely the word "or" causing me a problem

Help would be appreciated