04. (10 points) Explain the protection scheme for Unix in the folowing figure for Program.e, and mail rw-rw-r 1 pbg staff 31200 Sep 3 08:30 intro.ps rwxrwxr-x 2 pbg staff 512 Jul 8 09:35 doc/ 5pbg staff 512 Jul 8 09.33 private xrwx_2pbg student 512 Aug 314:13 student-proj rw rW-Tr lpbg staff 9423 Feb 24 2003 program.c rwxr-xr-x lpbg staff 20471 Feb 24 2003 program drwx-x-x 4pbg faculty 512 Jul 31 10:31 lib/ 3 pbg staff ?bg-staff 1024 Aug 29 06:52 512 Jul 8 09:35 mail/ test/ rwx 8