An environmental researcher claims that the mean amount of sulfur dioxide in the air in U.S. cities is 1.15 parts per billion. In a random sample of 134 U.S. cities, the mean amount of sulfur dioxide in the air is 0.93 parts per billion. Assume the population standard deviation is 2.62 parts per billion. At α = 0.01, is there enough evidence to reject the claim?

(a) Identify the claim and state H₀ and H_a, 

(b) Find the critical value(s) and identify the rejection region(s), (c) find the standardized test statistic z, 

(d) Decide whether to reject or fail to reject the null hypothesis, and

(e) Interpret the decision in the context of the original claim.