Translate the following inference to logic notation: For all x, x_8 is a soldier if and only if x_8 is a mechanic. For all x, x_8 is a mechanic if and only if x_8 is a soldier. Therefore for all x, x_8 is a soldier if and only if x_8 is a mechanic.
forall x: P(x) <-> Q(x). forall x: Q(x) <-> P(x). Therefore forall x: P(x) <-> Q(x).