Marie distributes toys for toddlers. She makes visits to households and gives away one toy only on visits for which the door is answered and a toddler is in residence. On any visit, the probability of the door being answered is 3/4, and the probability that there is a toddler in residence is 1/3. Assume that the events "Door answered" and "Toddler in residence" are independent and also that events related to different households are independent. a) Given that she has not given away her second toy by her third visit, what is the conditional probability that she will give away her second toy on her fifth visit? b) If she starts out with exactly six toys, what is the expected value of the number of houses with toddlers that Marie visits without leaving any toys (because the door was not answered) before she needs a new supply?