The lifetime of a light bulb is normally distributed with an average life of 500 hours and a standard deviation of 100 hours. If a company installs 5000 of these light bulbs, find the number of bulbs...

The lifetime of a light bulb is normally distributed with an average life of 500 hours and a standard deviation of 100 hours.  If a company installs 5000 of these light bulbs, find the number of bulbs that can be expected to last between 500 hours and 675 hours.