An ecologist randomly samples 20 plants of a specific species and measures their heights. He finds that this sample has a mean of 13 cm and a standard deviation of 3 cm. If we assume that the height measurements are normally distributed, find a 90% confidence interval for the mean height of all plants of this species. Then find the lower limit and upper limit of the 90% confidence interval. Carry your intermediate computations to at least three decimal places. Round your answers to one decimal place. (If necessary, consult a list of formulas.) Lower limit: X 5 ? Upper limit:]