A gardener wants to fence three sides of the yard in front of her house. She bought 60 m of fence and wants an area of about 400m^2. The
quadratic equation f(x) = 60x - 2x^2, where x is the width of the
yard in metres and f(x) is the area in square metres, gives the area
that can be enclosed. Determine the dimensions that will give the
desired area.