Answer
$\frac{1}{24}$
Work Step by Step
We know that $probability=\frac{\text{number of favourable outcomes}}{\text{number of all outcomes}}$
The number of all outcomes is $4!=24$ (same as $_4P_4$ because we place $4$ digits to $4$ places and the order matters)
There is $1$ "good outcome."
Hence the probability here is: $\frac{1}{24}$
