Math
posted by Alex .
A consumer buys n light bulbs, each of which has a lifetime that has a mean
of 800 hours, a standard deviation of 100 hours, and a normal distribution. A light bulb is replaced by another as soon as it burns out. Assuming independence of the lifetimes, find the smallest n so that the succession of light bulbs produces light for at
least 10,000 hours with a probability of 0.90.

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