A bottled water plant utilizes a production process designed to fill bottles with 20 ounces of water. The population of filling volumes is normally distributed with a standard deviation of 1.3 ounces. Periodically, process engineers take 20-bottle samples and compute the sample mean. a. What are the upper and lower control limits? b. Suppose the last five sample means were 19.4, 20.2, 20.5, 20.7, and 21.1 ounces. Is the process under control?