1. A computer has three main modules that have individual reliabilities of 0.70, 0.90, and 0.83. Because of recent failures, management is now considering adding redundancy. Determine the reliability of the system if the backup consists of an identical computer that operates as a whole rather than backing up individual sections. The single switch for the backup computer has a reliability of .96.

2. A DVD Burner has a mean time between failures of 84 weeks. Find the probability that the unit will last at least 92 weeks.

3. The useful life of an artificial heart valve is normally distributed with a mean of 49 months and a standard deviation of 7 months. Determine the probability that the valve will wear out within 35 month(s) of its installation (Find P( X < 35 ).

4. A DVD Burner has a mean time between failures of 83 weeks. Find the probability that the unit will fail between 66 and 89 weeks in other words, find P (66 < t < 89)