Construct an example of a sequence \(\{A_n\}_{n=1}^{\infty }\) such that:
(a) (i) \(\sum _n\mathbb {P}(A_n)=\infty \); and (ii) only finitely-many of the \(A_n\)’s occur with positive probability.
(b) (i) \(\sum _n\mathbb {P}(A_n)=\infty \); and (ii) infinitely-many of the \(A_n\)’s occur with positive probability.