设P(A)=0.5，P(B)=0.6，P(B|A反)=0.4，求P(AB)．

设P(A)=0.5，P(B)=0.6，P(B|A反)=0.4，求P(AB)．
【正确答案】：P(B|A反)=(P(B)-P(AB))/(1-P(A))
P(AB)=0.4