Answer
$1$
Work Step by Step
$P(n,r)$ denotes the number of permutations of a set of $n$ objects taken $r$ at a time and can be found as:
$$P(n,r)=\dfrac{n!}{(n-r)!}$$
using the formula above with $n=6$ and $r=0$ yields:
$$P(6,0)=\dfrac{6!}{(6-0)!}=\dfrac{6!}{6!}=1$$
