Find the critical point of the function. Then use the second derivative test to classify the nature of this point, if possible. (If an answer does not exist, enter DNE.) f(x, y) = 6 ? 7x2 ? 4y2 critical point (x, y) = classification ---Select--- Finally, determine the relative extrema of the function. (If an answer does not exist, enter DNE.) relative minimum value relative maximum value