Find Values Of $x$ And $y$ Such That Both $f_{x}(x, y)=0$ And $f_{y}(x, y)=0$

Multiple Choice

Find values of $x$ and $y$ such that both $f_{x}(x, y) =0$ and $f_{y}(x, y) =0$ .
- $f(x, y) =12 x y-4 x-4 y+9$

A) $x=-\frac{1}{3}, y=-\frac{1}{3}$
B) $x=3, y=3$
C) $\mathrm{x}=\frac{1}{3}, \mathrm{y}=\frac{1}{3}$
D) $x=-3, y=-3$