There lives a population of lemurs on an island which can either be healthy, be sick, or be dead. Each year, there is 0.2 probability that a healthy lemur gets sick and 0.1 probability that it dies; there is 0.3 probability that a sick lemur recovers and becomes healthy and 0.6 probability that it dies (and dead lemurs stay dead forever). a. An ecologist visits the island and observes that in 1990 there are 1000 healthy lemurs. Of that population, how many will still be alive in 5 years, in expectation? b. If the ecologist visits the island again in 1993, how many of the lemurs she observes from the original population will not have experienced sickness at any time since she last saw them?