Answer:
The length of the diagonal is 284 km
Step-by-step explanation:
1- we get the side length of the side:
We are given that the land has a square shape and an area of 40,404 km²
Area of square = (side)²
40,404 = (side)²
side = +√40,404
side = 201.007 km ≈ 201 km
2- we get the length of the diagonal:
Refer to the attach picture representing the area of land.
We can infer that the two side lengths along with the diagonal of the land form a right-angled triangle.
Therefore, to get the diagonal, we can apply the Pythagorean theorem as follows:

Diagonal = 284.2 ≈ 284 km
Hope this helps :)