If $P(A)=P(B)=x\: and \: P(A \cap B ) = P(A' \cap B')=\large\frac{1}{3}$ then x is equal to

Question

$\begin {array} {1 1} (A)\;\large\frac{1}{2} & \quad (B)\;\large\frac{1}{3} \\ (C)\;\large\frac{1}{4} & \quad (D)\;\large\frac{1}{6} \end {array}$