If $A$ and $B$ are two events such that $P ( A \cup B ) = P ( A \cap B )$, then the incorrect statement amongst the following statements is:\\
(1) $P ( A ) + P ( B ) = 1$\\
(2) $P \left( A \cap B ^ { \prime } \right) = 0$\\
(3) $A \& B$ are equally likely\\
(4) $P \left( A ^ { \prime } \cap B \right) = 0$