A normal random variable x has an unknown mean 
and standard deviation 
= 2.5. If the probability that x exceeds 7.5 is 0.8289, find 
.
______________
Definitions:
Narcolepsy
A persistent sleeping condition marked by excessive sleepiness during the day and abrupt sleep onset episodes.
REM Sleep
A sleep phase characterized by rapid eye movement, during which vivid dreams commonly occur. This stage is associated with increased brain activity.
Sleep Apnea
A sleep disorder characterized by pauses in breathing or periods of shallow breathing during sleep.
Insomnia
A sleep disorder characterized by difficulty in falling or staying asleep.
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