Complete the following problems using the 6 step procedure for testing statistical hypotheses.

#21 (8 points) The mean gross income of plumbers in the Salt Lake City area follows the normal probability distribution with a mean of $45,000 and a population standard devation of $3,000. A recent investigation by KYAK TV found, for a sample of 120 plumbers, the mean gross income was $45,500. At the .05 level of significance, is it reasonable to conclude that the mean income of the population of plumbers in Salt Lake City is NOT $45,000?