Probability of no life for star is (1-p), where p=5.0x10^-14. Therefore the

probability of no life for any of N stars is (1-p)^N.

Therefore life for at least one of N starts is:

P=1-(1-p)^N.

In the first case N=(100 10^9)(300 10^9) = 3 10 ^22.

In the second case N=N=(1 10^9)(10 10^9) = 1 10 ^19.

Now your problem is how to evaluate P (both of these numbers

are so close to 1 to not worry about the difference).

RonL