Imagine a rectangle box that cover most of the park and then count the squares on the left side and then the square on the top.
Left side = 8
Top side = 6
8 * 6 = 48
But notice there is a lot of space left over in our squares oo=n the left, right side, top, and bottom, so this tells us it is going to be under 48 and 45 more than likely. So I would estimate between 30 to 40 km^2