Looking at the attachment, we'll determine entire hexagon area with this formula:
area = apothem^2 *Number of sides * tan(180/n)
area = 17.32^2 * 6 * tan (30)
area = 299.9824 * 6 * 0.57735
area = 1,039.16903184
Now we subtract the triangle area (16*20 = 320)
shaded area = 1,039.16903184 -320 = 719.16903184
answer is D