Translate the following inference to logic notation: Richard is a writer if and only if Michael is listening to a song. Linda is working if and only if Richard is a writer. Michael is not sleeping. For all x, x_21 will sleep if and only if x_21 will listen to a song. Therefore Linda is not working or Charles is making tea.
p <-> P(a). q <-> p. ~Q(a). forall x: Q(x) <-> P(x). Therefore ~q or r.