Which of the following settings for umask ensures that new files have the default permissions -rw- r----- ?

A umask of 0017 would result in default file permissions of 666 - 017 = 650 (-rw-r-x---), which includes execute permission for the group.

0640 represents a permission mode itself, not a umask value; if used as a umask, it would drastically alter permissions in an unintended way.

A umask of 0038 is not a valid octal representation for permissions because '8' is not a valid digit in octal numbering.

Default permissions for new files are 666 (rw-rw-rw-). To achieve 640 (rw-r-----), the umask value is subtracted from the default. A umask of 027 subtracts 0 from owner (6-0=6), 2 from group (6-2=4), and 7 from others (6-7=0), resulting in 640.