Translate the following inference to logic notation: For all x, x_11 will read a book if and only if x_11 is a nurse. For all x, x_11 is a nurse if and only if x_11 will read a book. Therefore if Charles reads a book, then Charles is a nurse.
forall x: P(x) <-> Q(x). forall x: Q(x) <-> P(x). Therefore P(a) -> Q(a).