Answer
99.7% of light bulbs will have lifetimes between 441 and 759 hours.
Work Step by Step
The Empirical Rule says that, for a bell shaped distribution, about 99.7% of the data will be between μ-3σ and μ+3σ.
In this case:
$μ−3σ=600−3×53=441$
$μ+3σ=600+3×53=759$
