I would probably say (0,0) just because (5,0) falls on the x-axis and not on the y-axis and the other are just regular plotting coordinates. (0,0) is the only one that falls on the y-axis although it still falls on the x-axis as well
First draw the box with the diagonal, as you can see it is split into 2 equal right triangles. Now use the pythagorean theorem (a^2+b^2=c^2) to find the length of the diagonal
