What purpose would Linux file permissions set to rw$-$r$$r$--$ serve?

To prevent reading and writing for all users, and to prevent reading by groups and a specific user

To allow system administrators to read and write the file, and for users and all others to be able to read it

To allow all users to read and write the file, and for the group and owner to be able to read it

To allow the owner to read and write the file, and for the owner's group and others to be able to read it