Answer:
Split this complex polygon into parts to tackle this. I see two triangles (NML, HJK), one semicircle (PH), and one Rectangle (ONKH).
Explanation:
Rectangle: (distance between O and N) x (distance between O and H)
Semi Circle: [ (pi or (3.1415) ) x r or [distance between P and H] / 2) / 2]
Triangle: ( base x height) / 2