P(SAC) = P(S) * P(A|S) * P(C1|SA) = 1/2 * 1/3 * 1/3 = 1/18.
P(SAGF) = P(S) * P(A|S) * P(G|SA) = 1/2 * 1/3 * 2/3 = 2/18 = 1/9.