b) Mark and Helen are two new sysadmins hired by ITS to administer their Unix systems. i. Explain the strategy used by Unix systems to support extended access control lists. [15 marks] ii. The owner and group classes have read and write permissions on the /etc/passwd file. The other class doesn't have any permission to the file. Mark and Helen need read and write permissions to the file. Describe the extended ACLs for this system. [7 marks] c) Explain how ITS can use password file access control to thwart a password attack in their systems. [8 marks]