Elementary Statistics (12th Edition)

$\frac{1}{5040}$.
By using the factorian rule we can get the number of possibilities: $7!=7\times6\times5\times4\times3\times2\times1=5040$. We also know that $probability=\frac{number \ of \ good \ outcomes}{number\ of\ all\ outcomes}$, therefore $P=\frac{1}{5040}$.