In a health center, patients' ages are normally distributed with a mean of 50 years and a standard deviation of 20 years. There were 30 patients visited the center this morning. a. What is the probability that a single patient has an age over 60 years? b. What interval, centered at 50 years, will contain 92% of all possible values for the patients' ages? c. What is the sampling distribution of the average age of 30 patients in the health center? d. What is the probability that the 30 patients from this morning have an average age over 60 years