Translate the following inference to logic notation: Thomas is not a nurse. For all x, if x_7 were sad, then x_7 is a nurse. For all x, x_7 is sad if and only if x_7 is a nurse. Therefore Thomas is not sad.
~P(a). forall x: Q(x) -> P(x). forall x: Q(x) <-> P(x). Therefore ~Q(a).