An environmental group (Clear Air for All) which is concerned with air polluting industries argues that air pollution has risen significantly over the past year as regulations were released. They feel that the mean amount now exceeds 18 micrograms. Previous studies have shown a population standard deviation of 4.3 micrograms. The group collects air samples from 36 areas of the city and finds the mean particulate matter to be 20.5 micrograms per cubic meter. Test the groups claim at the .05 significance level. Be sure to show the claim, your null and alternative hypothesis and all computations and values. What do you conclude about the null hypothesis? What do you conclude about the claim?