4. Lifetimes of a certain brand of tires is approximately normally distributed with mean 38,520 miles and standard deviation 2975 miles a) In what range do the middle 95% of tire lifetimes lie? b) What proportion of tires last over 38,000 miles? c) What is the median life time of the tires? d) How far do the longest-lasting 4% of these tires roll? (What percentile are you finding here?) e) Customers get a refund if a tire has unacceptable tread that puts it in the bottom 11% of all tires. At what mileage is a customer no longer entitled to a refund?