Translate the following inference to logic notation: For all x, if y_4 climbs a mountain, then y_4 is taking a plane. For all x, y_4 will take a plane if and only if y_4 will make tea. Therefore for all x, if y_4 climbs a mountain, then y_4 is making tea.
forall x: P(x) -> Q(x). forall x: Q(x) <-> R(x). Therefore forall x: P(x) -> R(x).