5.
\includegraphics[max width=\textwidth, alt={}]{38c285f8-a542-42fb-aa4c-41adb9a8f63e-2_439_807_242_534}
The diagram shows the sector \(O A B\) of a circle, centre \(O\), in which \(\angle A O B = 2.5\) radians.
Given that the perimeter of the sector is 36 cm ,
- find the length \(O A\),
- find the perimeter and the area of the shaded segment.