The mean lifetime of certain tire is 30,000 miles and standard deviation is 2,500 miles.
a. If we suppose the mileages are normally distributed, approximately what percentage of all such tires will last between 22,500 and 37,500 miles?
b. If we assume nothing regarding the shape of the distribution, approximately what percentage of all such tires will last between 22,500 and 37,500 miles?
Please work