QUESTION 14 A design engineer wants to construct a sample mean chart for controlling the service life of a halogen headlamp his company produces. He knows from numerous previous samples that his service life is normally distributed with a mean of 500 hours and a standard deviation of 20 hours. On three recent batches, he tested service life on random samples of four headlamps with the results listed below. What is the sample mean service life for sample 2? Sample Service Life (hours) 495 500 505 500 1 2 525 515 505 515 3 470 480 460 470 a. 460 hours O b. 495 hours C. 500 hours d.515 hours e. 525 hours