Translate the following inference to logic notation: If it is cloudy, then Robert is sad. If it is late, then it is cloudy. If it is cloudy, then Mary is playing a game. Robert is not sad. If Mary plays a game, then it is late. Therefore Mary is not playing a game or Robert is reading a book.
p -> q. r -> p. p -> s. ~q. s -> r. Therefore ~s or t.