Express each of these system specifications using predicates, quantifiers, and logical connectives.

a$)$ At least one mail message, among the nonempty set

of messages, can be saved if there is a disk with more

than $10$ kilobytes of free space. b$)$ Whenever there is an active alert, all queued messages

are transmitted.

c$)$ The diagnostic monitor tracks the status of all systems

except the main console.

d$)$ Each participant on the conference call whom the host

of the call did not put on a special list was billed