A manufacturer of cookies and crackers does a small survey of the age at sale of one of its brands. A random sample of 33 retail markets in a particular region is chosen. In each store, the number of days since manufacture of the frontmost box of crackers is determined by a date code on the box. The data (age in days) from the 33 stores showed the sample mean to be 56.869 days, and the sample standard deviation to be 28.97 which almost precisely estimated the population standard deviation. Suppose the manufacturer wants to obtain a 90% confidence interval with a margin of error that depicts 5 days between the lowest and highest points of the interval. Assuming that the sample standard deviation does not change, how large a sample is needed? Show all work.