Translate the following inference to logic notation: For all x, x_7 is a taxi driver or x_7 will not sleep. For all x, x_7 will work if and only if x_7 will sleep. Therefore for all x, if x_7 works, then x_7 is a taxi driver.
forall x: P(x) or ~Q(x). forall x: R(x) <-> Q(x). Therefore forall x: R(x) -> P(x).