Answer to Question #315312 in Discrete Mathematics for Sheeren

Question

7. Express these system specifications using the proposi tions p "The message is scanned for viruses" and "The message was sent from an unknown system together with logical connectives (including negations).

a) "The message is scanned for viruses whenever the message was sent from an unknown system." b) "The message was sent from an unknown system but

it was not scanned for viruses. c) "It is necessary to scan the message for viruses when ever it was sent from an unknown system.

d) "When a message is not sent from an unknown system

it is not scanned for viruses.

Answer 1

q - "The message was sent from an unknown system"

a) $q\implies p$

b) $q \land \neg p$

c) $q\implies p$

d) $\neg q\implies \neg p$