World Travel City Photography

The inputs depend on the length of the perimeter:
(2) I = 4s, where I stands for the quantity of inputs. This equation shows that the perimeter is proportional to the length of a side.
So there are increasing returns to scale:
(3) O = I2 / 16. This equation (solving for s in (1) and substituting in (2)) shows that with twice the inputs, you produce quadruple the output.