A particular automobile costs an average of $18,855 in the Pacific Northwest. The (population) standard deviation of prices is $650. Assume the prices are normally distributed. (a) What is the probability of finding one automobile of this model at a cost of less than $18,500? (b) Suppose a random sample of 15 dealerships in Washington and Oregon is taken and their managers are asked what they charge for this automobile. What is the probability of getting a sample average cost of less than $18,500