Find the local maximum and minimum values and saddle point(s) of the function. If you have three-dimensional graphing software, graph the function with a domain and viewpoint that reveal all the important aspects of the function. (Enter your answers as a comma-separated list. If an answer does not exist, enter DNE.) 64 64 f = + + (X, y) xy X y local maximum value(s) DNE local minimum value(s) D saddle point(s) (x, y, f) = DNE Need Help? _