2) A regional CPA firm conducted an audit for a discount chain. One part of the audit involved developing an estimate for the mean dollar error in total charges that occur during the checkout process. They wish to develop a 90% confidence interval estimate for the population mean. A simple random sample of n = 20 is selected, with the following data (in dollars): 0.00 1.20 0.43 1.00 1.47 -0.36 -1.10 2.60 0.00 0.00 0.83 0.50 3.34 1.58 1.46 -1.70 0.83 1.99 0.00 1.34 a. Calculate the sample mean. b. Calculate the sample standard deviation. c. Develop a 90% confidence interval estimate for the population mean.