Find the area of the shaded figure

Many years ago, in the south pacific, there was a small island kingdom that was ruled by a kind and benevolent King. Each year, on the King's birthday, the residents of the island gave the King a new throne as token of their love and respect for him.

And each year, the King would put last years gift up in the attic of his small grass house. After many years of ruling the island, the weight of the large number of birthday presents stored up in the attic became too heavy and caused the house to collapse down on the King.

Moral to the story is: He who lives in grass house, shouldn't stow thrones.