Translate the following inference to logic notation: For all x, x_15 will read a book if and only if x_15 will drink water. If it is late, then Barbara is reading a book. If Barbara drinks water, then it is late. Therefore if it is late, then Barbara is drinking water.
forall x: P(x) <-> Q(x). p -> P(a). Q(a) -> p. Therefore p -> Q(a).