3. Differentiability and partial derivatives. Consider the function defined by for (z,y) (0,0) (a) Show that f is not continuous at (0,0) (b) Findå·¦(0,0) and fy(0,0) (be careful to follow the definition off closely). (c) Even thoughå·¦and fy exist at (0,0), why is f not differentiable at (0,0)?