Suppose that there exist three different types of components, with two units of each type. Each unit operates independently, and each type has probability pi of performing successfully. Either one or two systems can be built. One system can be assembled as follows: The two units of each type of component are put together in parallel, and the three types are then assembled to operate in series. Alternatively, two subsystems are assembled, each consisting of the three different types of components assembled in series. The final system is obtained by putting the two subsystems together in parallel. Which system has higher reliability?