A rectangular field with base x and height 2r is surmounted by two semicircular fields, as shown in the diagram below. The external perimeter of the fields (solid blue track) is 200 meters. Answer the following: a) Express the area A of the rectangular field (shaded green) as a function of r A (r ) = X b) Determine the maximum area enclosed by the rectangular field. (Type "pi" if you need it, or look in the MathPad Greek list. Decimal approximations are marked incorrect.) Maximum area = square meters X