A purchasing manager at a university is investigating which brand of LCD projector to purchase for equipping classrooms. Of major concern to her is the lifetime of the light bulbs used in the projectors. One company has published the following frequency distribution from a test of the lifetimes (in hours) of 42 bulbs used in its LCD projectors.

Bulb lifetime Frequency

(in hours)

700 to 749 4

750 to 799 7

800 to 849 12

850 to 899 8

900 to 949 7

950 to 999 4

Based on the frequency distribution, using the midpoint of each data class, estimate the mean lifetime for the light bulbs in the company's test. For your intermediate computations, use four or more decimal places, and round your answer to one decimal place.