Bag of potatoes are usually 10 pounds
-2 -10 -3
-7 0 -8
-6 -5 -4
That's the square, it was a fun puzzle :)
Let the side length of the square be x, then A = x^2
but diagonal (z) = sqrt(2x^2)
z^2 = 2x^2
x^2 = 1/2 z^2
Thus, A = 1/2 z^2
dA/dz = 1/2 (2z) = z
The rate of change is z.
When z = 4, the rate is 4.