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) = 3 - 2x + 4y - x2 - 4y2 local maximum value(s) local minimum value(s) saddle point(s) ( x, y, f ) =