Answer variants:
15.7
21.7
24.7
26.7
In the given figure, \(AB\) and \(CD\) are two diameters of a circle (with centre \(O\)) perpendicular to each other and \(OD\) is the diameter of the smaller circle. If \(OA = 4\) \(cm\), calculate the area of the shaded region.
The area of the shaded region \(cm^2\).