Hi. From Willey Statiscs book. Please make sure tables and formulas used are from there. thanks :)

Section 8.1, Exercise 7

The price of a head of iceberg lettuce varies greatly with the season and the geographic location of a store. During February a researcher contacts a random sample of 39 grocery stores across Australia and asks the produce manager of each to state the current price charged for a head of iceberg lettuce. Using the researcher's results that follow, construct a 99% confidence interval to estimate the mean price of a head of iceberg lettuce in February in Australia. Assume that is 0.205.