If A and B are two events such that $\;P(A) \cup P(B) = P(A) \cap P(B)\;$ , then the incorrect statement amongst the following statements is :

Question

$(a)\;A\;and\;B\;are\;equally\;likely\qquad(b)\;P(A \cap B^{'})=0 \qquad(c)\;P(A^{'} \cap B)=0 \qquad(d)\;P(A)+P(B)=1$