Do Pythagorean Theorem because a rectangle divided in diagonals form right triangles
A^2+b^2=C^2
Plug in the correct numbers and solve
A and B can be switched around but C is always the longest diagonal side which is called the hypotenuse not the Adjacent sides that form a right angle
So with correct solving you should get 5.
GFBH is the code
1 is -3,-2 which is G
2 is 3,4 which is F
3 is 2,0 which is B
4 is 1,-3 which is H
B I think if I’m wrong I sooooo sorry