A lamp has two bulbs, each of a type with an average lifetime of 6 hours. The probability density function for the lifetime of a bulb is f(t) =(1/6) e^{-t/6}, t is less than 0.

What is the probability that both of the bulbs will fail within 4 hours?

What is the probability that both of the bulbs will fail within 4 hours?

## This question was asked on Apr 28, 2010.

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