A company wants to test a randomly selected sample of n water specimens and estimate the mean daily rate of pollution produced by a mining operation. If the company wants a 95%confidence interval estimate with a margin of error of 1.6milligramsper liter(mg/L), how many water specimens are required in thesample? Assume prior knowledge indicates that pollution readings in water samples taken during a day are approximately normally distributed with a standard deviation equal to

9mg/L.