A.1) A new printing machine is tested about the number of printing errors per 5m² paper. It is assumed that the number of printing errors will have Poisson distribution with parameter I. a) If X1, X2,..., Xn is a random sample of size n, estimate the parameter of the distribution. b) The randomly selected 12 papers are inspected, and the number of printing errors are found as 2, 0, 0, 1, 1, 0, 1, 1, 2, 0, 1, and 0. Estimate the mean number of printing errors, and write down the distribution function. c) In order to estimate the distribution parameter with 0.3 error and 4% risk, find the minimum sample size.