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) = x3 - 3x + 3xy2 local maximum value(s) local minimum value(s) X saddle point(s) ( x, y, f ) =