A manager wants to construct a sample mean chart for controlling the service life of a product her company produces. She knows from numerous previous samples that this service life is normally distributed with a mean of 500 hours and a standard deviation of 20 hours. On three recent production batches, she tested service life on random samples of four headlamps, with these results: Sample 1, Service Life (hours): 495, 500, 505, 500; Sample 1, Service Life (hours): 525, 515, 505, 515; Sample 1, Service Life (hours): 470, 480, 460, 470. If he uses upper and lower control limits of 520 and 480 hours, on what sample(s) (if any) does service life appear to be out of control? Sample 1 Sample 2 Sample 3 both Sample 1 & 3 All samples are in control