After a ham is cured, it may be smoked to add flavor or to ensure it lasts longer. Typical grocery-store hams are smoked for a short period of time, whereas gourmet hams are usually smoked for at least one month. A random sample of 36 grocery-store hams was obtained, and the length of the smoking time was recorded for each. The mean was =140 hours. Assume = 8 hours.
b. Find a 95% confidence interval for the mean amount of time a grocery-store ham is smoked.