3.It is known that screws produced by a certain company will be defective with a probability 0.01. independently of each other. The company sells screws in packages of 10 and offers a money back guarantee that at most 1 of the 10 screws is defective. What proportion of packages sold must the company replace?2

4.Suppose that the number of typographical errors on a single page of the Oxford English Dictionary has a Poisson distribution with lambda = 0.5. Calculate the probability that there is at least one error on a given page.