Translate the following inference to logic notation: For all x, x_5 will take a plane or x_5 will write a letter. For all x, if x_5 takes a plane, then x is a writer. For all x, if x_5 writes a letter, then x is a writer. Therefore there is at least one x for which x is a writer.
forall x: P(x) or Q(x). forall x: P(x) -> R(x). forall x: Q(x) -> R(x). Therefore exists x: R(x).