[2.5] A system functions as long as both subsystems A and B are functioning. Subsystem A is composed of two components A 1 and A 2 and functions as long as either functions. Subsystem B is composed of two components B 1 and B 2 and functions as long as either functions. Subsystems A and B are independent. Components A 1 and A 2 are mutually exclusive. Components B 1 and B 2 are independent. If the probabilities that the components are functioning are: Find the probability that the system is functioning. .