The mean weight of trucks traveling on a particular section of 1-475 is not known. A state highway inspector needs to estimate the population mean. He selects and weighs a random sample of 49 trucks. The mean weight of the 49 trucks was 15.8 tons. Assume for purposes of this problem that the population standard deviation is known, and it is 3.8 tons. What is the 72% confidence interval for the population mean