This is a composite figure, so it will be easier to break it up into two shapes. We can split it into two rectangles, one measuring 17 by 13 km and another 9 by (40 - 13) km.
The area of the 17 by 13 rectangle is 17 * 13 = 221, while the area of the other rectangle is 9 * 27 = 243.
Add these two areas together and you get 243 + 221 = 464 km squared.