9-157. Consider the water quality data in Exercise 9-157. (a) Do these data support the claim that the mean concentra- tion of suspended solids does not exceed 30 parts per mil- lion? Use a = 0.05. (b) What is the P-value for the test in part (a)? (c) Does the normal distribution seem to be a reasonable model for these data? Perform an appropriate goodness-of- fit test to answer this