In a random sample of 25 calls made from the U.S. toJjapan by callers using skype during the past week, the average call lasted 21.4 minutes with a sample standard deviation of 5.1 minutes. Assume the population distribution of call times is normal. Build a 99% confidence interval estimate of the average call time for the population of calls represented by the sample ( that is the population of all calls made from the US to japan last week by callers using Skype)

Report the upper bound for your interval.