The Bureau of Labor Statistics reported that the average yearly income of dentists in the year 2009 was $110,000. A sample of 81 dentists, which was taken in 2010, showed an average yearly income of $120,000. Assume the standard deviation of the population of dentists in 2010 is $36,000. a. We want to test to determine if there has been a significant increase in the average yearly income of dentists. Provide the null and the alternative hypothesis. b. Compute the test statistic. c. Determine the p -value; and at 95% confidence, test the hypothesis.