A random sample of n = 15 heat pumps of a certain type yielded the following observations on lifetime (in years): 2.0 1.4 6.0 1.6 5.3 0.4 1.0 5.3 15.6 0.5 4.8 0.9 12.3 5.3 0.6 (a) Assume that the lifetime distribution is exponential and use an argument parallel to that of this example to obtain a 95% CI for expected (true average) lifetime. (Round your answers to two decimal places.) years (c) What is a 95% CI for the standard deviation of the lifetime distribution? [Hint: What is the standard deviation of an exponential random variable?] years