In the figure if PA and PB are tangents drawn to a circle Such that $\angle APB =30^{\circ}$ and chord AC is drawn parallel to the tangent PB, then $\angle ABC$=_____

Question

$\begin{array}{1 1} 60^{\circ}\\ 90^{\circ} \\30^{\circ} \\\text{none of the above} \end{array}$