Translate the following inference to logic notation: Sarah is running if and only if Richard is a writer. For all x, if x_15 listens to a song, then x_15 is running. Mary is not playing squash. Mary is playing squash if and only if Richard is a writer. Therefore Sarah is not listening to a song.
P(a) <-> p. forall x: Q(x) -> P(x). ~q. q <-> p. Therefore ~Q(a).