Find the local maximum and minimum values and saddle point(s) of the function. You are encouraged to use a calculator or computer to graph the function with a domain and viewpoint that reveals all the important aspects of the function. (Enter your answers as comma-separated lists. If an answer does not exist, enter DNE.) f(x, y) = (xy)(25 - xy) local maximum value(s) DNE local minimum value(s) saddle point(s) DNE (x, y) = DNE