What is the special permission in the group used for in the case below?

ubuntu@ubuntu:~$ ls $-$ld $/$var$/$mail

drwxrwsr$-$x $2$ root mail $4096$ Feb $32021/$var$/$mail

Question $12$Answer

a$.$

For all users belonging to mail to be able to write in the directory $/$var$/$mail

b$.$

For all files and folders created in $/$var$/$mail to belong to the group mail

c$.$

To execute $/$var$/$mail as root

d$.$

To execute $/$var$/$mail with the effective GID of mail