Nabisco company produces bags of crackers. The distribution of content weights of these bags is Normal with mean 18.0 oz and standard deviation 0.9 oz. We will randomly select n bags of crackers and weigh the contents of each bag selected.

How many bags should be selected so that the standard deviation of the sample mean is 0.1 ounces?

The length of human pregnancies from conception to birth varies according to a distribution that is approximately Normal with mean 260 days and standard deviation 12 days. The probability that the average pregnancy length for 6 randomly women exceeds 268 days is approximately