Find all local extreme values of the given function and identify each as a local maximum, local minimum, or saddle point. f(x.y) = 49x +21xy + 9y? O A. f(21,21)= 14,553, local maximum O B. f(21,21) = 14,553, local maximum; f(0,0) = 0, local minimum O C. f(7,3)= 2,923, saddle point; f(3,7)= 1,323, saddle point O D. f(0,0) = 0, local minimum