Past studies have shown that 60% of the children of parents who both smoke cigarettes will also end up smoking cigarettes, and only 20% of children whose parents do not smoke cigarettes will end up smoking cigarettes. In a family with four children, use the binomial probability model to determine

(a) the probability that none of the children become smokers given that both parents are smokers.

(b) the probability that none of the children become smokers given that none of the parents are smokers.