To help make a decision about expansion plans, the director of a music company needs to know how many compact discus teenagers buy annually. Accordingly, she commissions you, a recent employee, to conduct a survey. Suppose that you randomly selected 250 teenagers and asked each to report the number of CDs purchased in the previous 12 months. You found that the sample mean is 4.26 CDs and the sample standard deviation is 3 CDs. Construct a 95% confidence interval around the sample mean. Be sure to show whether you use the t- or z- value, and what value you use. Interpret the confidence interval in a single sentence. In another sentence, state why you used either the "t" or the "z".