Translate the following inference to logic notation: If Richard were a cashier, then John is not reading a book. John is reading a book. If Richard writes a letter, then Thomas is a taxi driver. If Thomas were a taxi driver, then Richard is writing a letter. For all x, y will write a letter if and only if y is a cashier. Therefore Thomas is not a taxi driver.
P(a) -> ~p. p. Q(a) -> q. q -> Q(a). forall x: Q(x) <-> P(x). Therefore ~q.