A table which is in a shape of a regular polygon is as shown in the figure below. If each of its sides is 5 units, what can be the area of the dotted portion ?

Question

$\begin{array}{1 1} (a)\;25 \sqrt{3} \\ (b)\;\dfrac{25}{2} \sqrt{3}\\ (c)\;50 \sqrt{3} \\(d)\;\dfrac{75}{2} \sqrt{3} \end{array}$