Preliminary road tests conducted by the Econotire's quality control division suggest that the lifetimes of its new, inexpensive radial are normally distributed with mean lifetime of 30,000 miles and standard deviation of 5,000 miles. Your store has just received a shipment of 1,000 such tires.
How many tires in your shipment do you expect to last between 27,500 and 33,800 miles?