Two chips are

being considered for use in a certain system.

The lifetime of chip 1

is

modelled

by a Gaussian random variable with mean 20,000 hours and standard

deviation

5000 hours. (The probability of negative lifetime is negligible.) The

lifetime of chip 2 is

also a

Gaussian random variable but with mean 22,000 hours

and standard deviation

000 hours.

Which chip is preferred if the target lifetime of

the system is 20,000 hours?

24,000 hours?