Burn Rubber, a tire manufacturer, produces tires that last, on average, 75,000 km with a standard deviation of 5,000 km. Tire mileage is approximately normally distributed.

(a) What percentage of tires will last between 78,000 and 87,500 km?

(b) What is the minimum mileage of the longest lasting 10% of the tires?

(c) If you randomly select a sample of 4 Burn Rubber tires, what is the probability that the sample mean mileage of the tires would be at least 85,000 km?