Since the squares are 10×10, 6 of them = 100×6=600in^2
There are 6 equilateral triangles around the hexagon, and the hexagon itself is made of 6 of those equilateral triangles. So 12× triangle's area will complete the total area.
Height of the triangle will split it into 2 30-60-90 triangles. So the h will be 5SR3, since the height will bisect the base (10) into 2 5's. And a 30-60-90 will have sides of x, xSR3, and 2x. Since x=5, the h will be 5SR3 = 8.66.
So area of the triangle:
1/2×b×h = 1/2×10×8.66 = 43.3
Now 12×43.3 = 519.62
Now add that to the 600 from the squares:
519.62 + 600 = 1,199.62 in^2
The correct answer is (C.)