Consider the following function. f (x, y) = (x -4) In(xy) (a) Find the critical point of f. If the critical point is (a, b) then enter 'a,b' (without the quotes) into the answer box. (b) Using your critical point in (a), find the value of D(a, b) from the Second Partials test that is used to classify the critical point. (c) Use the Second Partials test to classify the critical point from (a). Enter your answer symbolically as in these examples If the critical point is (a, b) then enter a,b' into the answer box. Enter your answer symbolically as in these examples Value of D(a, b). A) Saddle Point (B) Inconclusive (C) Relative Minimum (D) Relative Maximum Select v