Compute the partial derivative of the function $f(x,y)=5-6x2y-3x^{2}y$ at a point $(2,4).$

a$.$ Find $\frac{\text{d}\text{e}\text{l}\text{f}}{\text{d}\text{e}\text{l}\text{x}}$ at $(2,4)$

b$.$ Find $\frac{\text{d}\text{e}\text{l}\text{f}}{\text{d}\text{e}\text{l}\text{y}}$ at $(2,4).$

$f_x(2,4)=$

$($Simplify your answer.$)$

$f_y(2,1)=$

$$

$($Simplify your answer.$)$