Using diaries for many weeks, a study on the lifestyles of visually impaired students was conducted. The students kept track of many lifestyle variables including how many hours of sleep obtained on a typical day. Researchers found that visually impaired students averaged $8.41$ hours of sleep, with a standard deviation of $2.15$ hours. Assume that the number of hours of sleep for these visually impaired students is normally distributed.

(a) What is the probability that a visually impaired student gets less than $6.2$ hours of sleep?

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(b) What is the probability that a visually impaired student gets between $6.8$ and $10.84$ hours of sleep?

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