A soon-to-be-introduced cell phone has an expected service life that can be modeled by a normal

distribution with a mean of five years and a standard deviation of 0.6 year.

a. If the company offers a warranty of four years, what percentage of cell phones can be expected

to fail before that time?

b. What probability can you assign to a service life of (1) 5.9 years? (2) 6.2 years?