The lifetime of a battery is normally distributed with a known standard deviation of 20 hours. The mean of a sample of 49 batteries was 120 hours. Find a 99% confidence interval for the population mean. What is the UPPER BOUND? ______________________________ Note: Enter XXX.X AT LEAST ONE DIGIT BEFORE THE DECIMAL, ONE AFTER and round up. Thus, 347 is entered as 347.0, 3.52 is entered as 3.5, 0.2750 is entered as 0.3, -0.564 is entered as -0.6