If PA and PB are tangents from outside point P such that PA = 10 cm and $\angle{APB}= 60^{\circ}$. Find the length of chord AB.<br>

Question

$\begin{array}{1 1} (a)\;20\;cm \\ (b)\; 5\; cm \\ (c)\; 10\; cm \\ (d)\; 15\;cm \end{array}$