A study was done to estimate the mean annual growth in a population of Conuspennaceus trees in Hawaii. For those with an initial size of 2.41-2.60 centimeters, a sample of size 12 yielded a mean annual growth of .72 centimeter and a standard deviation of .31 centimeter. Find a 90% confidence interval for the population mean of annual growth (of those trees with an initial size of 2.41-2.60 centimeters).