If P(A∪B)=0.8P(A \cup B) = 0.8P(A∪B)=0.8 and P(A)=0.5P(A) = 0.5P(A)=0.5, what is P(B∩Ac)P(B \cap A^c)P(B∩Ac)?
0.3
0.5
0.2
0.4