Express each of these system specifications using predicates, quantifiers, and logical connectives.
- When there is less than 30 megabytes free on the hard disk, a warning message is sent to all users.
- No directories in the file system can be opened and no files can be closed when system errors have been detected.
- The file system cannot be backed up if there is a user currently logged on.
- Video on demand can be delivered when there are at least 8 megabytes of memory available and the connection speed is at least 56 kilobits per second.