Translate the following inference to logic notation: If it is late, then it is snowing. William is a mechanic or Mary is a lawyer. If William were a mechanic, then it is snowing. If Mary were a lawyer, then it is late. David is a bartender if and only if it is snowing. Therefore David is a bartender.
p -> q. r or s. r -> q. s -> p. t <-> q. Therefore t.