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6) In Smithville, data from different shoe outlets revealed that the average sales of shoes are $868 per shoe outlet. There were 88 outlets taken as a sample for a survey where the mean calculated was $25.6, and standard deviation was known to be $2.80. a) Using the above data, calculate a 95% condence interval for the average sale of shoes. (4 Marks ) b) Using the answer that you have found in part (a) above, illustrate the confidence intervals using a standard normal distribution graph (Bell shaped curve). (2 Marks)