please help Thank you The probability density function of X

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The probability density function of X, the lifetime of a certain type of vehicle (in years), is given by Determine k. What is P{X > 15)? Find the cdf function F(x). What is the median? What is the expected life time of this type of vehicle? What is the standard deviation of X? What is the probability that X is within one standard deviation from the mean? Now we randomly select 14 vehicles of this type. What is the probability that at least 3 vehicles will function for at least 15 years (i.e., the lifetime is at least 15 years)?

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