Find the Second-Order Partial Derivative $f_{x y}$ When $f(x, y)=10 x^{2} y^{4}-7 x^{3} y^{5}$

Multiple Choice

Find the second-order partial derivative.
-Find $f_{x y}$ when $f(x, y) =10 x^{2} y^{4}-7 x^{3} y^{5}$ .

A) $160 x y^{3}-21 x^{2} y^{4}$
B) $160 x y^{3}-105 x^{2} y^{4}$
C) $80 x y^{3}-105 x^{2} y^{4}$
D) $80 x y^{3}-21 x^{2} y^{4}$