The function f(r, y) = 9xy+ 3ry + 3ry has a critical point at the origin, (0, 0). %3D We know that: Szz = 18y, %3D fyy= 6z, and %3D fay = 18z +3+ 6y. %3D Which of the following statements is true? O A. The origin is a local max for f(a, y). O B. The origin is a local min for f(r, y). O C. There is not enough information to say what type of critical point it is. O D. The origin is a saddle point for f(x, y).