The circle shown in the figure has an area 20. BC is tangent to the circle with centre A at point B. If $AC = 2AB$, then what is the area of the shaded region ?

Question

$\begin{array}{1 1} (a)\;\text{15 sq. units}\\ (b)\; \text{15.67 sq. units} \\(c)\; \text{16 sq. units} \\ (d)\; \text{16.75 sq. units} \end{array}$