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.) f(X,y)=7)(4+2x2y2 local maximum value(s) local minimum value(s) saddle point(s) (X, y, f) =