In average there is one defect per 100 m of magnetic tape. (a) What is the probability that 150 m of tape have no defect? (b) Given that the first 100 m of tape had no defect what is the probability that the whole 150 m have no defect? (c) Given that the first 100 m of tape had at least one defect what is the probability that the whole 150 m have exactly two defects?