I saw an equation as like that:
$P(W) = P(W\mid R,S)+P(W\mid !R,S) + P(W\mid !R,S) + P(W\mid R,!S) + P(W\mid !R,!S)$
Which of these two statements are true?
$P(W) = P(W\mid R,S)P(R,S)+P(W\mid !R,S)\,P(!R,S) + P(W\mid !R,S)\,P(!R,S) + P(W\mid R,!S)\,P(R,!S) + P(W\,!R,!S)\,P(!R,!S)$ or $P(R,S) = P(R\mid S)\,P(S) = P(S\mid R)\,P(R).$
Is there any document for it?