Question: The time needed to do a test has been found to be normally distributed with a mean of 30 minutes and a standard deviation of

The time needed to do a test has been found to be normally distributed with a mean of 30 minutes and a standard deviation of 10 minutes. (NOTE: you must first define a random variable .) (a) What is the probability of completing the test in more than 20 minutes but less than 40 minutes? (b) If the probability of completing the test in T minutes or less is 0.8, find T

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