Let A and B be two events such that $P ( A') = 0.3 \: P(B)=0.4 \: and \: P(A \cap B') = 0.5$ then $P(B/A\: UB')=$

Question

$\begin {array} {1 1} (1)\;\large\frac{1}{2} & \quad (2)\;\large\frac{3}{4} \\ (3)\;\large\frac{1}{4} & \quad (4)\;\large\frac{3}{7} \end {array}$