Workout the following problems and show all necessary steps. Use Algebra. In a random sample of 40 refrigerators, the mean repair cost was $150. Assume the population standard deviation = $15.5.  a. Construct a 99% interval for the population mean repair cost. Interpret the results. b. Repeat exercise 1a, changing the sample size to n=60. Which confidence interval has a better estimate? Why? Explain? c. Repeat exercise 1a, using a population standard deviation of $19.5. Which confidence interval is wider? Explain.

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