Find the area under the standard normal distribution curve:

1. between z = 0 and z = -2.14
2. To the left of z = -1.39

An American family of four washes an average of 2000 pounds of clothes each year. The standard deviation of the distribution is 187.5 pounds.

3. Find the probability that a randomly selected family of four will be between 1980 and 1990 pounds.

Find the probability that the mean of a randomly selected sample of 50 families of four will be between 1980 and 1990 pounds.