'4-27. Let Xbe a normally distributed random variable with mean p 16 and stan dard deviation & 3. Find P(1 < X< 20). Also find P(17 < X< 19) and P(X > 15). 4-28. The time it takes an international telephone operator to place an overseas phone call is normally distributed with mean 45 seconds and standard deviation 10 seconds_'
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