Find the Indicated Partial Derivative $$f ( x , y ) = x ^ { 2 } y ^ { 4 } - 3 x ^ { 4 } y , f _ { m x }$$

Multiple Choice

Find the indicated partial derivative. $$f ( x , y ) = x ^ { 2 } y ^ { 4 } - 3 x ^ { 4 } y , f _ { m x }$$

A) $f _ { xx x } = 12 x ^ { 2 } y$
B) $f _ { xx x } = - 36 x y$
C) $f _ { xx x } = 3 x y$
D) $f _ { xxx } = - 72 x y$
E) $f _ { xx x } = - 3 x y$