Hey this was a question from an old test, can you guys please help me with this one?

5. (20 points) Posix Shared Memory 10 points - why might you want the shared memory segment to be at the same virtual address in each program 10 points When three programs share a block of memory, when is the memory returned to the system when the first program exits when the last program exits when returned explicitly by a program when the system reboots