## Precalculus (10th Edition)

$3024$.
The order matters here, so it is basically $P(9,4).$ We know that $P(n,r)=n(n-1)(n-2)...(n-k+1).$ Also $P(n,0)=1$ by convention. Hence $P(9,4)=9\cdot8\cdot7\cdot6=3024$.