Scores at a local high school on the American College Testing (ACT) college entrance exam follow the normal distribution with a mean of 18 and a standard deviation of 8. A guidance counselor takes a random sample of 20 students and calculates the mean score, .

(a) Calculate the mean and standard deviation of the sampling distribution of .

(b) Find the probability that a sample of 20 students has a mean score of 19.5 or more.