The mean income per person in the United States is $45,000, and the distribution of incomes follows a normal distribution.

The mean income per person in the United States is $45,000, and the distribution of incomes follows a normal distribution. A random sample of 17 residents of Wilmington, Delaware, had a mean of $55,000 with a standard deviation of $8,500. At the .10 level of significance, is that enough evidence to conclude that residents of Wilmington, Delaware, have more income than the national average?(a)