Customers arrive at a movie theater at the advertised movie time only to find that they have to sit through several prev

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Customers arrive at a movie theater at the advertised movie timeonly to find that they have to sit through several previews andprepreview ads before the movie starts. Many complain that the timedevoted to previews is too long. A preliminary sample conductedby The Wall Street Journal showed that thestandard deviation of the amount of time devoted to previews wasthree minutes. Use that as a planning value for the standarddeviation in answering the following questions.
a. If we want to estimate the populationmean time for previews at movie theaters with a margin of error of78 seconds, what sample size should be used? Assume 95%confidence.
b. If we want to estimate the populationmean time for previews at movie theaters with a margin of error of1 minute, what sample size should be used? Assume 95%confidence.