3. The number of companies making their initial public offering of stock (IPO) can be modeled by a Poisson distribution With a mean of 20 per month. (a) Use the normal approximation to nd the probability of 250 or more IPOs occurring in a year. Sketch the distribution and give your answer to four decimal places. (b) Why is it better to use the normal approximation instead of the Poisson distribution to answer (a) in this case