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The efficiency (in lumens per watt) of light bulbs of a certain type has population mean...

The efficiency (in lumens per watt) of light bulbs of a certain type has population mean 12.5 and standard deviation 0.5, according to production specifications. The specifications for a room in which eight of these bulbs are to be installed call for the average efficiency of the eight bulbs to exceed 13.

What should be the mean efficiency per bulb, in lumens per watt, if the specification for the room is to be met with a probability of 0.80? (Assume that the standard deviation of efficiency measurements remains at 0.5. Round your answer to two decimal places.)

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