Area Without Numbers

Geometry Level 3

Two right triangles, both with legs measuring $a$ and $b$ , where $a>b$ , are overlapping as the image above.

What is the area of the gray quadrilateral?

\frac{ab^2}{a+b}

\frac{b(a^2+b^2)}{a+b}

\frac{a(a^2+b^2)}{a+b}

\frac{b^2(a-b)}{a+b}

\frac{a^2 b^2}{(a+b)^2}