On its municipal website, the city of Tulsa states that the rate it charges per 5 CCF of residential water is $21.62. How do the residential water rates of other U.S. public utilities compare to Tulsa's rate? The file ResidentialWater contains the rate per 5 CCF of residential water for 42 randomly selected U.S. cities. 

a. Formulate hypotheses that can be used to determine whether the population mean rate per 5 CCF of residential water charged by U.S. public utilities differs from the $21.62 rate charged by Tulsa. 

b. What is the p-value for your hypothesis test in part (a)? 

c. At α = .05, can your null hypothesis be rejected? What is your conclusion? 

d. Repeat the preceding hypothesis test using the critical value approach.