Answer
$3024$.
Work Step by Step
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 $P(9,4)=9\cdot8\cdot7\cdot6=3024$.
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