For the years 19962012, the mean age of teachers in the United States was 40 years with a standard deviation of 11 years. Source: U.S. Bureau of Labor Statistics. a. If 75 teachers in the United States are randomly selected, what is the probability their mean age is less than 42.5 years old? b. If 75 teachers in the United States are randomly selected, what is the probability their mean age is greater than 42.5 years old? c. Would it be an unusual event if a random sample of 75 American teachers was conducted and their mean age was less than 27 years old? Explain