The average height of 4 year-old children is 40 inches with a standard deviation of 2.4 inches. If the distribution of heights follows a normal curve, what is the probability that the average height...

The average height of 4 year-old children is 40 inches with a standard deviation of 2.4 inches.

If the distribution of heights follows a normal curve, what is the probability that the average height of a sample of 9 of these children is less than 37.9 inches?