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) = xy + 12x - 8y local maximum value(s) [Select] local minimum value(s) [Select] saddle point(s), (x, y) = [Select]