A new car tire manufacturer estimates that from actual road tests, the mean mileage =58,400 kilometers and that the standard deviation is 8,000 kilometers. a. what percentage of the tires can be expected to last more than 64,000 kilometers? b. if 10 % of the tires do not give the required mileage and replacement tires will be given at a discount, what is the mileage value at this point?