UKMT Senior Mathematical Challenge, 2016

Michael was walking in Marrakesh when he saw a tiling formed by tessellating the square tile as shown. The tile has four lines of symmetry and the length of each side is 8 cm. The length of $XY$ is 2 cm. The point $Z$ is such that $XZ$ is a straight line and $YZ$ is parallel to sides of the square. What is the area of the central grey octagon?

(A) $6\text{ cm}^2$ (B) $7\text{ cm}^2$ (C) $8\text{ cm}^2$ (D) $9\text{ cm}^2$ (E) $10\text{ cm}^2$