2. Consider a system comprising four components (A, B, C and D) connected as in the gure below. \"-1- The system is working if there is a path through working components from left to right. Suppose that components fail independently and the time to failure for each component has an exponential distribution with a mean of two years. Let T denote the time of failure for the system. (:1) Determine an expression for the probability that the system is working at time t, that is PG" > t). Hence1 give the probability density function for the time to failure of the System. - (b) Determine the mean, variance and moment generating function of the time to fail for the system