Suppose the life of a particular brand of calculator battery is approximately normally distributed with a mean of 75 hours and a standard deviation of 9 hours.
Complete parts a through c.
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Part 1
a. What is the probability that a single battery randomly selected from the population will have a life between 70 and 80 ​hours?
​P(70≤x≤80​)=enter your response here
​(Round to four decimal places as​ needed.)