3.(1)设A,B,C是三个事件,且 P(A)=P(B)=P(C)=1/4,P(AB)=P(BC)=0,P(AC)=1/8,求A,B,C至少有一个发生的概率.(2)已知 P(A)=1/2,P(B)=1/3,P(C)=1/5,P(AB)=1/10,P(AC)=1/15,P(BC)=1/20,P(ABC)=1/30,求 A cup B, overline (AB),A cup B cup C, overline (AB)C, overline (AB) cup C 的概率.(3)已知 P(A)=1/2,(i)若A,B互不相容,求 P( overline (AB)),(ii)若P(AB)=1/8,求P( overline (AB)).

(1) $P(A \cup B \cup C) = \frac{5}{8}$ (2) $P(A \cup B) = \frac{11}{15}$，$P(\overline{AB}) = \frac{4}{15}$，$P(A \cup B \cup C) = \frac{17}{20}$，$P(\overline{AB}C) = \frac{7}{60}$，$P(\overline{AB} \cap C) = \frac{7}{60}$，$P(\overline{AB} \cup C) = \frac{7}{20}$ (3) (i) $P(A\overline{B}) = \frac{1}{2}$，(ii) $P(A\overline{B}) = \frac{3}{8}$ \[ \boxed{ \begin{array}{ccc} \text{(1) } \frac{5}{8} \\ \text{(2) } \frac{11}{15}, \frac{4}{15}, \frac{17}{20}, \frac{7}{60}, \frac{7}{60}, \frac{7}{20} \\ \text{(3) } \frac{1}{2}, \frac{3}{8} \end{array} } \]