Two standby subsystems (A and B) and (C and D) are placed in parallel. The unit E should be in series with the two standby subsystems. Assume time to failure of A, B, C, D, and E are exponentially distributed and switching is perfect for the standby systems: If Lambda_a = Lambda_b = Lambda_c = Lambda_d = 10^-3 per hour determine the reliability of each standby subsystem (that is reliability (A and B) and reliability (C and D)). As a designer, if you are asked to select unit E such that its contribution to the failure of the whole system is less than 10 percents of the total system failure probability for a mission of t= 1000 h, what should be the minimum acceptable failure rate for unit E