Hi

Let's call the length of wire bent into the shape of a circle. is the perimeter of the circle and it is linked to its radius by . Thus the area of the circle is

Let's do the same thing for the square : let's call the length of wire bent into the shape of a square. is the perimeter of the square thus the length of one of its side is and its area is

As the length of wire is , . The area of the two shapes can be given in function of :

The problem boils down to finding the maximum and the minimum of the function for . (because )

Can you take it from here ?