Question: Estimating Length of Car Ownership: A NAPA Auto Parts supplier wants information about how long car owners plan to keep their cars. A simple random sample of 25 car owners results in `x = 7.01 years and s =3.74 years, respectively (based on data from a Roper poll). Assume that the sample is drawn from a normally distributed population.

a) Find a 95% confidence interval estimate of the population mean

b) Find a 95% confidence interval estimate of the population standard deviation.

c) If several years pass and you want to conduct a new survey to estimate the mean length of time that car owners plan to keep their cars, how many randomly selected car owners must you survey? Assume you want 99% confidence that the sample mean is within 0.25 year (or 3 months) of the population mean, and also assume that s = 3.74 years (based on the latest result)