An educational psychologist wishes to know the mean number of words a third grader can read per minute. She wants to make an estimate at the 80% level of confidence. For a sample of 518 third graders, the mean words per minute read was 26.5. Assume a population standard deviation of 4.2. Construct the confidence interval for the mean number of words a third grader can read per minute. Round your answers to one decimal place.