If $P(A)=\large\frac{1}{12}\: P(B)=\large\frac{5}{12}\: and \: P(B/A) = \large\frac{1}{15}$ then $P(A \cup B )$ is equal to

Question

$\begin {array} {1 1} (A)\;\large\frac{89}{180} & \quad (B)\;\large\frac{90}{180} \\ (C)\;\large\frac{91}{180} & \quad (D)\;\large\frac{92}{180} \end {array}$