3. Given the function f (x, y) = 23 - y3 - 3xy + 4, which of the following statements is true, for a particular a and b (which you must calculate)? A. (a, a) is a maximum and (-b, b) is a minimum B. (a, a) is a minimum and (-b, b) is a saddle point C. (a, a) is a saddle point and (-b, b) is a minimum D. (a, a) is a saddle point and (-6, 6) is a maximum