12. We have 100 components that we will put in use in a sequential fashion.

That is, component 1 is initially put in use, and upon failure it is replaced by component 2, which is itself replaced upon failure by component 3, and so on. If the lifetime of component i is exponentially distributed with mean 10 + 1/10, i = 1,..., 100, estimate the probability that the total life of all components will exceed 1200. Now repeat when the life distribution of component i is uniformly distributed over (0, 20 + 1/5), i = 1,..., 100.