Solution :
Let the probability laser works = p
The probability that the system works = [tex]$P(\text{all three component works}) = p^3 $[/tex]
= 0.99
Therefore, p = 0.9967
Now for the above probability critical z = -2.72
Hence, the mean life is equal to = [tex]10,000 + 2.72 \times 600[/tex]
= [tex]10,000+1632[/tex]
[tex]=11,632[/tex]
