Translate the following inference to logic notation: For all x, x_6 will drive a car or x_6 will not write a letter. For all x, if x_6 were a doctor, then x_6 is writing a letter. For all x, if x_6 drives a car, then x_6 is a doctor. Therefore for all x, x_6 will drive a car if and only if x_6 is a doctor.
forall x: P(x) or ~Q(x). forall x: R(x) -> Q(x). forall x: P(x) -> R(x). Therefore forall x: P(x) <-> R(x).