Find the limit, if it exists, or type DNE if it does not exist.

A. $\displaystyle\lim_{(x, y) \rightarrow (0, 0)} \frac{(x + 6y)^2}{x^2 + 36y^2} =$

B. $\displaystyle \lim_{(x, y) \rightarrow (0, 0)} \frac{6x^3 + 2y^3}{x^2 + y^2} =$
(Hint for B: use polar coordinates, that is $x = r\cos(\theta), y = r \sin(\theta)$ )