Determine which of the following are critical points of f (x, y) = 4x' y+xyty'+3 A: (0, 0) B: C: 6 216 O a) Only B and C are critical points O b) All are critical points O c) None are critical points O d) Only B is a critical point O e) Only A and B are critical points O f) Only C is a critical point O g) Only A is a critical point O h) Only A and C are critical points