An experiment designed to test the potency of a drug on 20 rats. Last animal studies have shown that a 10 mg dose of the drug is lethal 5% of the time within the first 4 hours; of the animals alive at 4 hours, 10% will die in the next 4 hours.
What is the probability that 3 or more rats will die in the next 4 hours?
What is the probability that 0 rats will die in the 8 hour period?
What is the probability that 2 rats will die within the 8 hour period?