The metropolitan airport commission is considering establishing limits on noise pollution around a local airport. At the present time, the noise level per jet takeoff in one neighborhood near the airport is approximately normally distributed with a mean of 100 decibels and a standard deviation of 6 decibels.

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A) what is the probability of a randomly chosen score to be no more than 85?

B) Suppose a random sample of 40 scores is selected, what is the probability that the mean score is at most 99?

C) Suppose 95% of scores are contained in an interval symmetrically around the mean. Find this interval.

D) what is the probability of a randomly chosen score to be at least 90?