A strange octagon

Geometry Level 5

ABCD is a square with a side length of $3 \sqrt{3}$ . AED, DGC, AHB and BFC are equilateral triangles.
The area of the polygon IJKLMNOP is $a + b \sqrt{3}$ , where $a$ and $b$ are rational numbers.
What is the value of $a+b$ ?