Presume that data were collected for 10000 sets of automobile brakes. The mileage at which each set had been 80% worn through was recorded. The average was 62700 as well as the standard deviation was 10400 miles.
(a) Explain what fraction of brakes is expected to be 80% worn in less than 45800 miles?
(b) Explain what fraction is expected to be 80% worn at a mileage between 60 000 and 70 000 miles?