According to the U.S. Centers for Disease Control and Prevention, Americans 85 years of age and older experience flu-associated respiratory and circulatory illness at an annual rate of approximately 1200 cases per 100,000 persons. If a rural county has 500 seniors in this age group, what is the probability that no more than 5 of them will experience such an illness during the coming year? If, in such a county, 15 seniors in this age group were to come down with such an illness during the coming year, would this be considered rather unusual? Explain your conclusion.