A design engineer wants to construct a mean chart for controlling the service life of a halogen headlamp his company produces. He tested service life on randomly picked three samples with four headlamps each, with these results: Sample 1 2 3 4 Service Time (hours) 1 2 3 4 5 800 900 1000 900 800 900 700 900 900 800 800 900 900 1000 1000 900 900 900 900 900 What is the sample mean for Sample 1? 850 800 1000 900 @ 880