Conditional probability with and without replacement

Conditional probability with and without replacement

A sample of size $r$ is taken from a population of $n$ elements. Find the
probability that none
of the $N$ prescribed elements will be included in the sample, assuming
the sampling to be
a) without
b) with replacement
..


Compare the numerical value for the two methods, when
(i) n=100, r=N=3
and
(ii) n=100, r=N=10
..