Let A1, A2, and A3 be events, and let Bi represent either Ai or its complement A~i. Then there are eight possible choices for the triple (B1,B2,B3). Prove that the events A1, A2, A3 are independent if and only if
P(B1∩B2∩B3)=P(B1)P(B2)P(B3),
for all eight of the possible choices for the triple (B1,B2,B3).